MICROSOFT SQL
Chapter 1: Getting started with Microsoft SQL Server
Version Release Date SQL Server 2017 2017-10-01
SQL Server 2016 2016-06-01 SQL Server 2014 2014-03-18
SQL Server 2012 2011-10-11
SQL Server 2008 R2 2010-04-01
SQL Server 2008 2008-08-06 SQL Server 2005 2005-11-01
SQL Server 2000 2000-11-01
Section 1.1: INSERT / SELECT / UPDATE / DELETE: the basics of Data Manipulation Language
Data Manipulation Language (DML for short) includes operations such as INSERT, UPDATE and DELETE:
-- Create a table HelloWorld
CREATE TABLE HelloWorld (
Id INT IDENTITY, Description VARCHAR(1000) )
-- DML Operation INSERT, inserting a row into the table INSERT INTO HelloWorld (Description) VALUES ('Hello World')
-- DML Operation SELECT, displaying the table SELECT * FROM HelloWorld
-- Select a specific column from table SELECT Description FROM HelloWorld
-- Display number of records in the table SELECT Count(*) FROM HelloWorld
-- DML Operation UPDATE, updating a specific row in the table UPDATE HelloWorld SET Description = 'Hello, World!' WHERE Id = 1
-- Selecting rows from the table (see how the Description has changed after the update?) SELECT * FROM HelloWorld
-- DML Operation - DELETE, deleting a row from the table DELETE FROM HelloWorld WHERE Id = 1
-- Selecting the table. See table content after DELETE operation
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SELECT * FROM HelloWorld
In this script we're creating a table to demonstrate some basic queries.
The following examples are showing how to query tables:
USE Northwind; GO SELECT TOP 10 * FROM Customers ORDER BY CompanyName
will select the first 10 records of the Customer table, ordered by the column CompanyName from the database Northwind (which is one of Microsoft's sample databases, it can be downloaded from here):
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Note that Use Northwind; changes the default database for all subsequent queries. You can still reference the database by using the fully qualified syntax in the form of [Database].[Schema].[Table]:
SELECT TOP 10 * FROM Northwind.dbo.Customers ORDER BY CompanyName
SELECT TOP 10 * FROM Pubs.dbo.Authors ORDER BY City
This is useful if you're querying data from different databases. Note that dbo, specified "in between" is called a schema and needs to be specified while using the fully qualified syntax. You can think of it as a folder within your database. dbo is the default schema. The default schema may be omitted. All other user defined schemas need to be specified.
If the database table contains columns which are named like reserved words, e.g. Date, you need to enclose the column name in brackets, like this:
-- descending order SELECT TOP 10 [Date] FROM dbo.MyLogTable ORDER BY [Date] DESC
The same applies if the column name contains spaces in its name (which is not recommended). An alternative syntax is to use double quotes instead of square brackets, e.g.:
-- descending order SELECT top 10 "Date" from dbo.MyLogTable order by "Date" desc
is equivalent but not so commonly used. Notice the difference between double quotes and single quotes: Single quotes are used for strings, i.e.
-- descending order SELECT top 10 "Date" from dbo.MyLogTable where UserId='johndoe'
order by "Date" desc
is a valid syntax. Notice that T-SQL has a N prefix for NChar and NVarchar data types, e.g.
SELECT TOP 10 * FROM Northwind.dbo.Customers WHERE CompanyName LIKE N'AL%' ORDER BY CompanyName
returns all companies having a company name starting with AL (% is a wild card, use it as you would use the asterisk in a DOS command line, e.g. DIR AL*). For LIKE, there are a couple of wildcards available, look here to find out more details.
Joins
Joins are useful if you want to query fields which don't exist in one single table, but in multiple tables. For example: You want to query all columns from the Region table in the Northwind database. But you notice that you require also the RegionDescription, which is stored in a different table, Region. However, there is a common key, RgionID which you can use to combine this information in a single query as follows (Top 5 just returns the first 5 rows, omit it to get all rows):
SELECT TOP 5 Territories.*,
Regions.RegionDescription FROM Territories INNER JOIN Region
ON Territories.RegionID=Region.RegionID ORDER BY TerritoryDescription
will show all columns from Territories plus the RegionDescription column from Region. The result is ordered by TerritoryDescription.
Table Aliases
When your query requires a reference to two or more tables, you may find it useful to use a Table Alias. Table aliases are shorthand references to tables that can be used in place of a full table name, and can reduce typing and editing. The syntax for using an alias is:
<TableName> [as] <alias>
Where as is an optional keyword. For example, the previous query can be rewritten as:
SELECT TOP 5 t.*,
r.RegionDescription FROM Territories t INNER JOIN Region r
ON t.RegionID = r.RegionID ORDER BY TerritoryDescription
Aliases must be unique for all tables in a query, even if you use the same table twice. For example, if your Employee table included a SupervisorId field, you can use this query to return an employee and his supervisor's name:
SELECT e.*,
s.Name as SupervisorName -- Rename the field for output FROM Employee e INNER JOIN Employee s
ON e.SupervisorId = s.EmployeeId
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WHERE e.EmployeeId = 111
Unions
As we have seen before, a Join adds columns from different table sources. But what if you want to combine rows from different sources? In this case you can use a UNION. Suppose you're planning a party and want to invite not only employees but also the customers. Then you could run this query to do it:
SELECT FirstName+' '+LastName as ContactName, Address, City FROM Employees UNION SELECT ContactName, Address, City FROM Customers
It will return names, addresses and cities from the employees and customers in one single table. Note that duplicate rows (if there should be any) are automatically eliminated (if you don't want this, use a UNION ALL instead). The column number, column names, order and data type must match across all the select statements that are part of the union - this is why the first SELECT combines FirstName and LastName from Employee into ContactName.
Table Variables
It can be useful, if you need to deal with temporary data (especially in a stored procedure), to use table variables: The difference between a "real" table and a table variable is that it just exists in memory for temporary processing.
Example:
DECLARE @Region TABLE (
RegionID int, RegionDescription NChar(50) )
creates a table in memory. In this case the @ prefix is mandatory because it is a variable. You can perform all DML operations mentioned above to insert, delete and select rows, e.g.
INSERT INTO @Region values(3,'Northern') INSERT INTO @Region values(4,'Southern')
But normally, you would populate it based on a real table like
INSERT INTO @Region SELECT * FROM dbo.Region WHERE RegionID>2;
which would read the filtered values from the real table dbo.Region and insert it into the memory table @Region - where it can be used for further processing. For example, you could use it in a join like
SELECT * FROM Territories t JOIN @Region r on t.RegionID=r.RegionID
which would in this case return all Northern and Southern territories. More detailed information can be found here. Temporary tables are discussed here, if you are interested to read more about that topic.
NOTE: Microsoft only recommends the use of table variables if the number of rows of data in the table variable are less than 100. If you will be working with larger amounts of data, use a temporary table, or temp table, instead.
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Section 1.2: SELECT all rows and columns from a table
Syntax:
SELECT * FROM table_name
Using the asterisk operator * serves as a shortcut for selecting all the columns in the table. All rows will also be selected because this SELECT statement does not have a WHERE clause, to specify any filtering criteria.
This would also work the same way if you added an alias to the table, for instance e in this case:
SELECT * FROM Employees AS e
Or if you wanted to select all from a specific table you can use the alias + " .* ":
SELECT e.*, d.DepartmentName FROM Employees AS e
INNER JOIN Department AS d
ON e.DepartmentID = d.DepartmentID
Database objects may also be accessed using fully qualified names:
SELECT * FROM [server_name].[database_name].[schema_name].[table_name]
This is not necessarily recommended, as changing the server and/or database names would cause the queries using fully-qualified names to no longer execute due to invalid object names.
Note that the fields before table_name can be omitted in many cases if the queries are executed on a single server, database and schema, respectively. However, it is common for a database to have multiple schema, and in these cases the schema name should not be omitted when possible.
Warning: Using SELECT * in production code or stored procedures can lead to problems later on (as new columns are added to the table, or if columns are rearranged in the table), especially if your code makes simple assumptions about the order of columns, or number of columns returned. So it's safer to always explicitly specify column names in SELECT statements for production code.
SELECT col1, col2, col3 FROM table_name
Section 1.3: UPDATE Specific Row
UPDATE HelloWorlds SET HelloWorld = 'HELLO WORLD!!!' WHERE Id = 5
The above code updates the value of the field "HelloWorld" with "HELLO WORLD!!!" for the record where "Id = 5" in HelloWorlds table.
Note: In an update statement, It is advised to use a "where" clause to avoid updating the whole table unless and until your requirement is different.
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Section 1.4: DELETE All Rows
DELETE FROM Helloworlds
This will delete all the data from the table. The table will contain no rows after you run this code. Unlike DROP TABLE, this preserves the table itself and its structure and you can continue to insert new rows into that table.
Another way to delete all rows in table is truncate it, as follow:
TRUNCATE TABLE HelloWords
Difference with DELETE operation are several:
Truncate operation doesn't store in transaction log file 1. If exists IDENTITY field, this will be reset 2. TRUNCATE can be applied on whole table and no on part of it (instead with DELETE command you can 3.
associate a WHERE clause)
Restrictions Of TRUNCATE
Cannot TRUNCATE a table if there is a FOREIGN KEY reference 1. If the table is participated in an INDEXED VIEW 2. If the table is published by using TRANSACTIONAL REPLICATION or MERGE REPLICATION 3. It will not fire any TRIGGER defined in the table 4.
[sic]
Section 1.5: Comments in code
Transact-SQL supports two forms of comment writing. Comments are ignored by the database engine, and are meant for people to read.
Comments are preceded by -- and are ignored until a new line is encountered:
-- This is a comment SELECT * FROM MyTable -- This is another comment WHERE Id = 1;
Slash star comments begin with /* and end with */. All text between those delimiters is considered as a comment block.
/* This is a multi-line comment block. */ SELECT Id = 1, [Message] = 'First row' UNION ALL SELECT 2, 'Second row' /* This is a one liner */ SELECT 'More';
Slash star comments have the advantage of keeping the comment usable if the SQL Statement loses new line characters. This can happen when SQL is captured during troubleshooting.
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Slash star comments can be nested and a starting /* inside a slash star comment needs to be ended with a */ to be valid. The following code will result in an error
/* SELECT * FROM CommentTable WHERE Comment = '/*' */
The slash star even though inside the quote is considered as the start of a comment. Hence it needs to be ended with another closing star slash. The correct way would be
/* SELECT * FROM CommentTable WHERE Comment = '/*' */ */
Section 1.6: PRINT
Display a message to the output console. Using SQL Server Management Studio, this will be displayed in the messages tab, rather than the results tab:
PRINT 'Hello World!';
Section 1.7: Select rows that match a condition
Generally, the syntax is:
SELECT <column names> FROM <table name> WHERE <condition>
For example:
SELECT FirstName, Age FROM Users WHERE LastName = 'Smith'
Conditions can be complex:
SELECT FirstName, Age FROM Users WHERE LastName = 'Smith' AND (City = 'New York' OR City = 'Los Angeles')
Section 1.8: UPDATE All Rows
A simple form of updating is incrementing all the values in a given field of the table. In order to do so, we need to define the field and the increment value
The following is an example that increments the Score field by 1 (in all rows):
UPDATE Scores SET score = score + 1
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This can be dangerous since you can corrupt your data if you accidentally make an UPDATE for a specific Row with an UPDATE for All rows in the table.
Section 1.9: TRUNCATE TABLE
TRUNCATE TABLE Helloworlds
This code will delete all the data from the table Helloworlds. Truncate table is almost similar to Delete from Table code. The difference is that you can not use where clauses with Truncate. Truncate table is considered better than delete because it uses less transaction log spaces.
Note that if an identity column exists, it is reset to the initial seed value (for example, auto-incremented ID will restart from 1). This can lead to inconsistency if the identity columns is used as a foreign key in another table.
Section 1.10: Retrieve Basic Server Information
SELECT @@VERSION
Returns the version of MS SQL Server running on the instance.
SELECT @@SERVERNAME
Returns the name of the MS SQL Server instance.
SELECT @@SERVICENAME
Returns the name of the Windows service MS SQL Server is running as.
SELECT serverproperty('ComputerNamePhysicalNetBIOS');
Returns the physical name of the machine where SQL Server is running. Useful to identify the node in a failover cluster.
SELECT * FROM fn_virtualservernodes();
In a failover cluster returns every node where SQL Server can run on. It returns nothing if not a cluster.
Section 1.11: Create new table and insert records from old table
SELECT * INTO NewTable FROM OldTable
Creates a new table with structure of old table and inserts all rows into the new table.
Some Restrictions
You cannot specify a table variable or table-valued parameter as the new table. 1. You cannot use SELECT...INTO to create a partitioned table, even when the source table is 2.
partitioned. SELECT...INTO does not use the partition scheme of the source table; instead, the new table is created in the default filegroup. To insert rows into a partitioned table, you must first create the partitioned table and then use the INSERT INTO...SELECT FROM statement. Indexes, constraints, and triggers defined in the source table are not transferred to the new table, 3.
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nor can they be specified in the SELECT...INTO statement. If these objects are required, you can create them after executing the SELECT...INTO statement. Specifying an ORDER BY clause does not guarantee the rows are inserted in the specified order. 4.
When a sparse column is included in the select list, the sparse column property does not transfer to the column in the new table. If this property is required in the new table, alter the column definition after executing the SELECT...INTO statement to include this property. When a computed column is included in the select list, the corresponding column in the new table 5.
is not a computed column. The values in the new column are the values that were computed at the time SELECT...INTO was executed.
[sic]
Section 1.12: Using Transactions to change data safely
Whenever you change data, in a Data Manipulation Language(DML) command, you can wrap your changes in a transaction. DML includes UPDATE, TRUNCATE, INSERT and DELETE. One of the ways that you can make sure that you're changing the right data would be to use a transaction.
DML changes will take a lock on the rows affected. When you begin a transaction, you must end the transaction or all objects being changed in the DML will remain locked by whoever began the transaction. You can end your transaction with either ROLLBACK or COMMIT. ROLLBACK returns everything within the transaction to its original state. COMMIT places the data into a final state where you cannot undo your changes without another DML statement.
Example:
--Create a test table
USE [your database] GO CREATE TABLE test_transaction (column_1 varchar(10)) GO
INSERT INTO
dbo.test_transaction
( column_1 ) VALUES
( 'a' )
BEGIN TRANSACTION --This is the beginning of your transaction
UPDATE dbo.test_transaction SET column_1 = 'B' OUTPUT INSERTED.* WHERE column_1 = 'A'
ROLLBACK TRANSACTION --Rollback will undo your changes
--Alternatively, use COMMIT to save your results
SELECT * FROM dbo.test_transaction --View the table after your changes have been run
DROP TABLE dbo.test_transaction
Notes:
This is a simplified example which does not include error handling. But any database operation can fail and
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hence throw an exception. Here is an example how such a required error handling might look like. You should never use transactions without an error handler, otherwise you might leave the transaction in an unknown state. Depending on the isolation level, transactions are putting locks on the data being queried or changed. You need to ensure that transactions are not running for a long time, because they will lock records in a database and can lead to deadlocks with other parallel running transactions. Keep the operations encapsulated in transactions as short as possible and minimize the impact with the amount of data you're locking.
Section 1.13: Getting Table Row Count
The following example can be used to find the total row count for a specific table in a database if table_name is replaced by the the table you wish to query:
SELECT COUNT(*) AS [TotalRowCount] FROM table_name;
It is also possible to get the row count for all tables by joining back to the table's partition based off the tables' HEAP (index_id = 0) or cluster clustered index (index_id = 1) using the following script:
SELECT [Tables].name AS [TableName],
SUM( [Partitions].[rows] ) AS [TotalRowCount] FROM sys.tables AS [Tables] JOIN sys.partitions AS [Partitions]
ON [Tables].[object_id] = [Partitions].[object_id] AND [Partitions].index_id IN ( 0, 1 ) --WHERE [Tables].name = N'table name' /* uncomment to look for a specific table */ GROUP BY [Tables].name;
This is possible as every table is essentially a single partition table, unless extra partitions are added to it. This script also has the benefit of not interfering with read/write operations to the tables rows'.
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Chapter 2: Data Types
This section discusses the data types that SQL Server can use, including their data range, length, and limitations (if any.)
Section 2.1: Exact Numerics
There are two basic classes of exact numeric data types - Integer, and Fixed Precision and Scale.
Integer Data Types
bit tinyint smallint int bigint
Integers are numeric values that never contain a fractional portion, and always use a fixed amount of storage. The range and storage sizes of the integer data types are shown in this table:
Data type Range Storage bit 0 or 1 1 bit **
tinyint 0 to 255 1 byte
smallint -2^15 (-32,768) to 2^15-1 (32,767) 2 bytes
int -2^31 (-2,147,483,648) to 2^31-1 (2,147,483,647) 4 bytes bigint -2^63 (-9,223,372,036,854,775,808) to 2^63-1 (9,223,372,036,854,775,807) 8 bytes
Fixed Precision and Scale Data Types
numeric decimal smallmoney money
These data types are useful for representing numbers exactly. As long as the values can fit within the range of the values storable in the data type, the value will not have rounding issues. This is useful for any financial calculations, where rounding errors will result in clinical insanity for accountants.
Note that decimal and numeric are synonyms for the same data type.
Data type Range Storage Decimal [(p [, s])] or Numeric [(p [, s])] -10^38 + 1 to 10^38 - 1 See Precision table
When defining a decimal or numeric data type, you may need to specify the Precision [p] and Scale [s].
Precision is the number of digits that can be stored. For example, if you needed to store values between 1 and 999, you would need a Precision of 3 (to hold the three digits in 100). If you do not specify a precision, the default precision is 18.
Scale is the number of digits after the decimal point. If you needed to store a number between 0.00 and 999.99, you would need to specify a Precision of 5 (five digits) and a Scale of 2 (two digits after the decimal point). You must specify a precision to specify a scale. The default scale is zero.
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The Precision of a decimal or numeric data type defines the number of bytes required to store the value, as shown below:
Precision Table
Precision Storage bytes 1 - 9 5
10-19 9
20-28 13
29-38 17
Monetary Fixed Data Types
These data types are intended specifically for accounting and other monetary data. These type have a fixed Scale of 4 - you will always see four digits after the decimal place. For most systems working with most currencies, using a numeric value with a Scale of 2 will be sufficient. Note that no information about the type of currency represented is stored with the value.
Data type Range Storage money -922,337,203,685,477.5808 to 922,337,203,685,477.5807 8 bytes
smallmoney -214,748.3648 to 214,748.3647 4 bytes
Section 2.2: Approximate Numerics
float [(n)] real
These data types are used to store floating point numbers. Since these types are intended to hold approximate numeric values only, these should not be used in cases where any rounding error is unacceptable. However, if you need to handle very large numbers, or numbers with an indeterminate number of digits after the decimal place, these may be your best option.
Data type Range Size float -1.79E+308 to -2.23E-308, 0 and 2.23E-308 to 1.79E+308 depends on n in table below
real -3.40E + 38 to -1.18E - 38, 0 and 1.18E - 38 to 3.40E + 38 4 Bytes
n value table for float numbers. If no value is specified in the declaration of the float, the default value of 53 will be used. Note that float(24) is the equivalent of a real value.
n value Precision Size 1-24 7 digits 4 bytes
25-53 15 digits 8 bytes
Section 2.3: Date and Time
These types are in all versions of SQL Server
datetime smalldatetime
These types are in all versions of SQL Server after SQL Server 2012
date
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datetimeoffset datetime2 time
Section 2.4: Character Strings
char varchar text
Section 2.5: Unicode Character Strings
nchar nvarchar ntext
Section 2.6: Binary Strings
binary varbinary image
Section 2.7: Other Data Types
cursor timestamp hierarchyid uniqueidentifier sql_variant xml table Spatial Types
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Chapter 3: Converting data types
Section 3.1: TRY PARSE
Version ≥ SQL Server 2012
It converts string data type to target data type(Date or Numeric).
For example, source data is string type and we need to covert to date type. If conversion attempt fails it returns NULL value.
Syntax: TRY_PARSE (string_value AS data_type [ USING culture ])
String_value – This is argument is source value which is NVARCHAR(4000) type. Data_type – This argument is target data type either date or numeric. Culture – It is an optional argument which helps to convert the value to in Culture format. Suppose you want to display the date in French, then you need to pass culture type as ‘Fr-FR’. If you will not pass any valid culture name, then PARSE will raise an error.
DECLARE @fakeDate AS varchar(10); DECLARE @realDate AS VARCHAR(10); SET @fakeDate = 'iamnotadate'; SET @realDate = '13/09/2015';
SELECT TRY_PARSE(@fakeDate AS DATE); --NULL as the parsing fails
SELECT TRY_PARSE(@realDate AS DATE); -- NULL due to type mismatch
SELECT TRY_PARSE(@realDate AS DATE USING 'Fr-FR'); -- 2015-09-13
Section 3.2: TRY CONVERT
Version ≥ SQL Server 2012
It converts value to specified data type and if conversion fails it returns NULL. For example, source value in string format and we need date/integer format. Then this will help us to achieve the same.
Syntax: TRY_CONVERT ( data_type [ ( length ) ], expression [, style ] )
TRY_CONVERT() returns a value cast to the specified data type if the cast succeeds; otherwise, returns null.
Data_type - The datatype into which to convert. Here length is an optional parameter which helps to get result in specified length. Expression - The value to be convert Style - It is an optional parameter which determines formatting. Suppose you want date format like “May, 18 2013” then you need pass style as 111.
DECLARE @sampletext AS VARCHAR(10); SET @sampletext = '123456'; DECLARE @ realDate AS VARCHAR(10); SET @realDate = '13/09/2015’; SELECT TRY_CONVERT(INT, @sampletext); -- 123456 SELECT TRY_CONVERT(DATETIME, @sampletext); -- NULL SELECT TRY_CONVERT(DATETIME, @realDate, 111); -- Sep, 13 2015
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Section 3.3: TRY CAST
Version ≥ SQL Server 2012
It converts value to specified data type and if conversion fails it returns NULL. For example, source value in string format and we need it in double/integer format. Then this will help us in achieving it.
Syntax: TRY_CAST ( expression AS data_type [ ( length ) ] )
TRY_CAST() returns a value cast to the specified data type if the cast succeeds; otherwise, returns null.
Expression - The source value which will go to cast. Data_type - The target data type the source value will cast. Length - It is an optional parameter that specifies the length of target data type.
DECLARE @sampletext AS VARCHAR(10); SET @sampletext = '123456';
SELECT TRY_CAST(@sampletext AS INT); -- 123456 SELECT TRY_CAST(@sampletext AS DATE); -- NULL
Section 3.4: Cast
The Cast() function is used to convert a data type variable or data from one data type to another data type.
Syntax
CAST ( [Expression] AS Datatype)
The data type to which you are casting an expression is the target type. The data type of the expression from which you are casting is the source type.
DECLARE @A varchar(2) DECLARE @B varchar(2)
set @A='25a' set @B='15'
Select CAST(@A as int) + CAST(@B as int) as Result --'25a' is casted to 25 (string to int) --'15' is casted to 15 (string to int)
--Result
--40
DECLARE @C varchar(2) = 'a'
select CAST(@C as int) as Result --Result
--Conversion failed when converting the varchar value 'a' to data type int.
Throws error if failed
Section 3.5: Convert
When you convert expressions from one type to another, in many cases there will be a need within a stored procedure or other routine to convert data from a datetime type to a varchar type. The Convert function is used for
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such things. The CONVERT() function can be used to display date/time data in various formats. Syntax
CONVERT(data_type(length), expression, style)
Style - style values for datetime or smalldatetime conversion to character data. Add 100 to a style value to get a four-place year that includes the century (yyyy).
select convert(varchar(20),GETDATE(),108)
13:27:16
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Chapter 4: User Defined Table Types
User defined table types (UDT for short) are data types that allows the user to define a table structure. User defined table types supports primary keys, unique constraints and default values.
Section 4.1: creating a UDT with a single int column that is also a primary key
CREATE TYPE dbo.Ids as TABLE (
Id int PRIMARY KEY )
Section 4.2: Creating a UDT with multiple columns
CREATE TYPE MyComplexType as TABLE (
Id int, Name varchar(10) )
Section 4.3: Creating a UDT with a unique constraint:
CREATE TYPE MyUniqueNamesType as TABLE (
FirstName varchar(10), LastName varchar(10), UNIQUE (FirstName,LastName) )
Note: constraints in user defined table types can not be named.
Section 4.4: Creating a UDT with a primary key and a column with a default value:
CREATE TYPE MyUniqueNamesType as TABLE (
FirstName varchar(10), LastName varchar(10), CreateDate datetime default GETDATE() PRIMARY KEY (FirstName,LastName) )
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Chapter 5: SELECT statement
In SQL, SELECT statements return sets of results from data collections like tables or views. SELECT statements can be used with various other clauses like WHERE, GROUP BY, or ORDER BY to further refine the desired results.
Section 5.1: Basic SELECT from table
Select all columns from some table (system table in this case):
SELECT * FROM sys.objects
Or, select just some specific columns:
SELECT object_id, name, type, create_date FROM sys.objects
Section 5.2: Filter rows using WHERE clause
WHERE clause filters only those rows that satisfy some condition:
SELECT * FROM sys.objects WHERE type = 'IT'
Section 5.3: Sort results using ORDER BY
ORDER BY clause sorts rows in the returned result set by some column or expression:
SELECT * FROM sys.objects ORDER BY create_date
Section 5.4: Group result using GROUP BY
GROUP BY clause groups rows by some value:
SELECT type, count(*) as c FROM sys.objects GROUP BY type
You can apply some function on each group (aggregate function) to calculate sum or count of the records in the group.
type c SQ 3 S 72
IT 16
PK 1
U 5
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Section 5.5: Filter groups using HAVING clause
HAVING clause removes groups that do not satisfy condition:
SELECT type, count(*) as c FROM sys.objects GROUP BY type HAVING count(*) < 10
type c SQ 3 PK 1
U 5
Section 5.6: Returning only first N rows
TOP clause returns only first N rows in the result:
SELECT TOP 10 * FROM sys.objects
Section 5.7: Pagination using OFFSET FETCH
OFFSET FETCH clause is more advanced version of TOP. It enables you to skip N1 rows and take next N2 rows:
SELECT * FROM sys.objects ORDER BY object_id OFFSET 50 ROWS FETCH NEXT 10 ROWS ONLY
You can use OFFSET without fetch to just skip first 50 rows:
SELECT * FROM sys.objects ORDER BY object_id OFFSET 50 ROWS
Section 5.8: SELECT without FROM (no data souce)
SELECT statement can be executed without FROM clause:
declare @var int = 17;
SELECT @var as c1, @var + 2 as c2, 'third' as c3
In this case, one row with values/results of expressions are returned.
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Chapter 6: Alias Names in SQL Server
Here is some of different ways to provide alias names to columns in Sql Server
Section 6.1: Giving alias after Derived table name
This is a weird approach most of the people don't know this even exist.
CREATE TABLE AliasNameDemo(id INT,firstname VARCHAR(20),lastname VARCHAR(20))
INSERT INTO AliasNameDemo VALUES (1,'MyFirstName','MyLastName')
SELECT * FROM (SELECT firstname + ' ' + lastname
FROM AliasNameDemo) a (fullname)
Demo
Section 6.2: Using AS
This is ANSI SQL method works in all the RDBMS. Widely used approach.
CREATE TABLE AliasNameDemo (id INT,firstname VARCHAR(20),lastname VARCHAR(20))
INSERT INTO AliasNameDemo VALUES (1,'MyFirstName','MyLastName')
SELECT FirstName +' '+ LastName As FullName FROM AliasNameDemo
Section 6.3: Using =
This is my preferred approach. Nothing related to performance just a personal choice. It makes the code to look clean. You can see the resulting column names easily instead of scrolling the code if you have a big expression.
CREATE TABLE AliasNameDemo (id INT,firstname VARCHAR(20),lastname VARCHAR(20))
INSERT INTO AliasNameDemo VALUES (1,'MyFirstName','MyLastName')
SELECT FullName = FirstName +' '+ LastName FROM AliasNameDemo
Section 6.4: Without using AS
This syntax will be similar to using AS keyword. Just we don't have to use AS keyword
CREATE TABLE AliasNameDemo (id INT,firstname VARCHAR(20),lastname VARCHAR(20))
INSERT INTO AliasNameDemo VALUES (1,'MyFirstName','MyLastName')
SELECT FirstName +' '+ LastName FullName FROM AliasNameDemo
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Chapter 7: NULLs
In SQL Server, NULL represents data that is missing, or unknown. This means that NULL is not really a value; it's better described as a placeholder for a value. This is also the reason why you can't compare NULL with any value, and not even with another NULL.
Section 7.1: COALESCE ()
COALESCE () Evaluates the arguments in order and returns the current value of the first expression that initially does not evaluate to NULL.
DECLARE @MyInt int -- variable is null until it is set with value. DECLARE @MyInt2 int -- variable is null until it is set with value. DECLARE @MyInt3 int -- variable is null until it is set with value.
SET @MyInt3 = 3
SELECT COALESCE (@MyInt, @MyInt2 ,@MyInt3 ,5) -- Returns 3 : value of @MyInt3.
Although ISNULL() operates similarly to COALESCE(), the ISNULL() function only accepts two parameters - one to check, and one to use if the first parameter is NULL. See also ISNULL, below
Section 7.2: ANSI NULLS
From MSDN
In a future version of SQL Server, ANSI_NULLS will always be ON and any applications that explicitly set the option to OFF will generate an error. Avoid using this feature in new development work, and plan to modify applications that currently use this feature.
ANSI NULLS being set to off allows for a =/<> comparison of null values.
Given the following data:
id someVal ---- 0 NULL 1 1 2 2
And with ANSI NULLS on, this query:
SELECT id FROM table WHERE someVal = NULL
would produce no results. However the same query, with ANSI NULLS off:
set ansi_nulls off
SELECT id FROM table
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WHERE someVal = NULL
Would return id 0.
Section 7.3: ISNULL()
The IsNull() function accepts two parameters, and returns the second parameter if the first one is null.
Parameters:
check expression. Any expression of any data type. 1. replacement value. This is the value that would be returned if the check expression is null. The replacement 2.
value must be of a data type that can be implicitly converted to the data type of the check expression.
The IsNull() function returns the same data type as the check expression.
DECLARE @MyInt int -- All variables are null until they are set with values.
SELECT ISNULL(@MyInt, 3) -- Returns 3.
See also COALESCE, above
Section 7.4: Is null / Is not null
Since null is not a value, you can't use comparison operators with nulls. To check if a column or variable holds null, you need to use is null:
DECLARE @Date date = '2016-08-03'
The following statement will select the value 6, since all comparisons with null values evaluates to false or unknown:
SELECT CASE WHEN @Date = NULL THEN 1
WHEN @Date <> NULL THEN 2 WHEN @Date > NULL THEN 3 WHEN @Date < NULL THEN 4 WHEN @Date IS NULL THEN 5 WHEN @Date IS NOT NULL THEN 6
Setting the content of the @Date variable to null and try again, the following statement will return 5:
SET @Date = NULL -- Note that the '=' here is an assignment operator!
SELECT CASE WHEN @Date = NULL THEN 1
WHEN @Date <> NULL THEN 2 WHEN @Date > NULL THEN 3 WHEN @Date < NULL THEN 4 WHEN @Date IS NULL THEN 5 WHEN @Date IS NOT NULL THEN 6
Section 7.5: NULL comparison
NULL is a special case when it comes to comparisons.
Assume the following data.
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id someVal ---- 0 NULL 1 1 2 2
With a query:
SELECT id FROM table WHERE someVal = 1
would return id 1
SELECT id FROM table WHERE someVal <> 1
would return id 2
SELECT id FROM table WHERE someVal IS NULL
would return id 0
SELECT id FROM table WHERE someVal IS NOT NULL
would return both ids 1 and 2.
If you wanted NULLs to be "counted" as values in a =, <> comparison, it must first be converted to a countable data type:
SELECT id FROM table WHERE ISNULL(someVal, -1) <> 1
OR
SELECT id FROM table WHERE someVal IS NULL OR someVal <> 1
returns 0 and 2
Or you can change your ANSI Null setting.
Section 7.6: NULL with NOT IN SubQuery
While handling not in sub-query with null in the sub-query we need to eliminate NULLS to get your expected results
create table #outertable (i int) create table #innertable (i int)
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insert into #outertable (i) values (1), (2),(3),(4), (5) insert into #innertable (i) values (2), (3), (null)
select * from #outertable where i in (select i from #innertable) --2 --3 --So far so good
select * from #outertable where i not in (select i from #innertable) --Expectation here is to get 1,4,5 but it is not. It will get empty results because of the NULL it executes as {select * from #outertable where i not in (null)}
--To fix this select * from #outertable where i not in (select i from #innertable where i is not null) --you will get expected results --1 --4 --5
While handling not in sub-query with null be cautious with your expected output
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Chapter 8: Variables
Section 8.1: Declare a Table Variable
DECLARE @Employees TABLE (
EmployeeID INT NOT NULL PRIMARY KEY, FirstName NVARCHAR(50) NOT NULL, LastName NVARCHAR(50) NOT NULL, ManagerID INT NULL )
When you create a normal table, you use CREATE TABLE Name (Columns) syntax. When creating a table variable, you use DECLARE @Name TABLE (Columns) syntax.
To reference the table variable inside a SELECT statement, SQL Server requires that you give the table variable an alias, otherwise you'll get an error:
Must declare the scalar variable "@TableVariableName".
i.e.
DECLARE @Table1 TABLE (Example INT) DECLARE @Table2 TABLE (Example INT)
/* -- the following two commented out statements would generate an error: SELECT * FROM @Table1 INNER JOIN @Table2 ON @Table1.Example = @Table2.Example
SELECT * FROM @Table1 WHERE @Table1.Example = 1 */
-- but these work fine: SELECT * FROM @Table1 T1 INNER JOIN @Table2 T2 ON T1.Example = T2.Example
SELECT * FROM @Table1 Table1 WHERE Table1.Example = 1
Section 8.2: Updating variables using SELECT
Using SELECT, you can update multiple variables at once.
DECLARE @Variable1 INT, @Variable2 VARCHAR(10) SELECT @Variable1 = 1, @Variable2 = 'Hello' PRINT @Variable1 PRINT @Variable2
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1
Hello
When using SELECT to update a variable from a table column, if there are multiple values, it will use the last value. (Normal order rules apply - if no sort is given, the order is not guaranteed.)
CREATE TABLE #Test (Example INT) INSERT INTO #Test VALUES (1), (2)
DECLARE @Variable INT SELECT @Variable = Example FROM #Test ORDER BY Example ASC
PRINT @Variable
2
SELECT TOP 1 @Variable = Example FROM #Test ORDER BY Example ASC
PRINT @Variable
1
If there are no rows returned by the query, the variable's value won't change:
SELECT TOP 0 @Variable = Example FROM #Test ORDER BY Example ASC
PRINT @Variable
1
Section 8.3: Declare multiple variables at once, with initial values
DECLARE
@Var1 INT = 5, @Var2 NVARCHAR(50) = N'Hello World', @Var3 DATETIME = GETDATE()
Section 8.4: Updating a variable using SET
DECLARE @VariableName INT SET @VariableName = 1 PRINT @VariableName
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1
Using SET, you can only update one variable at a time.
Section 8.5: Updating variables by selecting from a table
Depending on the structure of your data, you can create variables that update dynamically.
DECLARE @CurrentID int = (SELECT TOP 1 ID FROM Table ORDER BY CreateDate desc)
DECLARE @Year int = 2014 DECLARE @CurrentID int = (SELECT ID FROM Table WHERE Year = @Year)
In most cases, you will want to ensure that your query returns only one value when using this method.
Section 8.6: Compound assignment operators
Version ≥ SQL Server 2008 R2
Supported compound operators:
+= Add and assign
-= Subtract and assign
*= Multiply and assign
/= Divide and assign
%= Modulo and assign
&= Bitwise AND and assign
^= Bitwise XOR and assign
|= Bitwise OR and assign
Example usage:
DECLARE @test INT = 42; SET @test += 1; PRINT @test; --43 SET @test -= 1; PRINT @test; --42 SET @test *= 2 PRINT @test; --84 SET @test /= 2; PRINT @test; --42
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Chapter 9: Dates
Section 9.1: Date & Time Formatting using CONVERT
You can use the CONVERT function to cast a datetime datatype to a formatted string.
SELECT GETDATE() AS [Result] -- 2016-07-21 07:56:10.927
You can also use some built-in codes to convert into a specific format. Here are the options built into SQL Server:
DECLARE @convert_code INT = 100 -- See Table Below SELECT CONVERT(VARCHAR(30), GETDATE(), @convert_code) AS [Result]
@convert_code Result 100 "Jul 21 2016 7:56AM"
101 "07/21/2016"
102 "2016.07.21"
103 "21/07/2016"
104 "21.07.2016" 105 "21-07-2016"
106 "21 Jul 2016"
107 "Jul 21, 2016"
108 "07:57:05"
109 "Jul 21 2016 7:57:45:707AM" 110 "07-21-2016"
111 "2016/07/21"
112 "20160721"
113 "21 Jul 2016 07:57:59:553" 114 "07:57:59:553" 120 "2016-07-21 07:57:59"
121 "2016-07-21 07:57:59.553"
126 "2016-07-21T07:58:34.340"
127 "2016-07-21T07:58:34.340" 130 "16 ???? 1437 7:58:34:340AM"
131 "16/10/1437 7:58:34:340AM"
SELECT GETDATE() AS [Result] -- 2016-07-21 07:56:10.927 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),100) AS [Result] -- Jul 21 2016 7:56AM UNION SELECT CONVERT(VARCHAR(30),GETDATE(),101) AS [Result] -- 07/21/2016 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),102) AS [Result] -- 2016.07.21 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),103) AS [Result] -- 21/07/2016 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),104) AS [Result] -- 21.07.2016 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),105) AS [Result] -- 21-07-2016 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),106) AS [Result] -- 21 Jul 2016 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),107) AS [Result] -- Jul 21, 2016 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),108) AS [Result] -- 07:57:05 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),109) AS [Result] -- Jul 21 2016 7:57:45:707AM UNION SELECT CONVERT(VARCHAR(30),GETDATE(),110) AS [Result] -- 07-21-2016 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),111) AS [Result] -- 2016/07/21 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),112) AS [Result] -- 20160721 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),113) AS [Result] -- 21 Jul 2016 07:57:59:553 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),114) AS [Result] -- 07:57:59:553 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),120) AS [Result] -- 2016-07-21 07:57:59 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),121) AS [Result] -- 2016-07-21 07:57:59.553
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UNION SELECT CONVERT(VARCHAR(30),GETDATE(),126) AS [Result] -- 2016-07-21T07:58:34.340 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),127) AS [Result] -- 2016-07-21T07:58:34.340 UNION SELECT CONVERT(VARCHAR(30),GETDATE(),130) AS [Result] -- 16 ???? 1437 7:58:34:340AM UNION SELECT CONVERT(VARCHAR(30),GETDATE(),131) AS [Result] -- 16/10/1437 7:58:34:340AM
Section 9.2: Date & Time Formatting using FORMAT
Version ≥ SQL Server 2012
You can utilize the new function: FORMAT().
Using this you can transform your DATETIME fields to your own custom VARCHAR format.
Example
DECLARE @Date DATETIME = '2016-09-05 00:01:02.333'
SELECT FORMAT(@Date, N'dddd, MMMM dd, yyyy hh:mm:ss tt')
Monday, September 05, 2016 12:01:02 AM
Arguments
Given the DATETIME being formatted is 2016-09-05 00:01:02.333, the following chart shows what their output would be for the provided argument.
Argument Output yyyy 2016 yy 16
MMMM September
MM 09
M 9
dddd Monday ddd Mon
dd 05
d 5
HH 00 H 0 hh 12
h 12
mm 01
m 1
ss 02 s 2
tt AM
t A
fff 333
ff 33 f 3
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You can also supply a single argument to the FORMAT() function to generate a pre-formatted output:
DECLARE @Date DATETIME = '2016-09-05 00:01:02.333'
SELECT FORMAT(@Date, N'U')
Monday, September 05, 2016 4:01:02 AM
Single Argument Output D Monday, September 05, 2016
d 9/5/2016
F Monday, September 05, 2016 12:01:02 AM f Monday, September 05, 2016 12:01 AM
G 9/5/2016 12:01:02 AM
g 9/5/2016 12:01 AM
M September 05 O 2016-09-05T00:01:02.3330000
R Mon, 05 Sep 2016 00:01:02 GMT
s 2016-09-05T00:01:02
T 12:01:02 AM
t 12:01 AM U Monday, September 05, 2016 4:01:02 AM
u 2016-09-05 00:01:02Z
Y September, 2016
Note: The above list is using the en-US culture. A different culture can be specified for the FORMAT() via the third parameter:
DECLARE @Date DATETIME = '2016-09-05 00:01:02.333'
SELECT FORMAT(@Date, N'U', 'zh-cn')
2016年9月5日 4:01:02
Section 9.3: DATEADD for adding and subtracting time periods
General syntax:
DATEADD (datepart , number , datetime_expr)
To add a time measure, the number must be positive. To subtract a time measure, the number must be negative.
Examples
DECLARE @now DATETIME2 = GETDATE(); SELECT @now; --2016-07-21 14:39:46.4170000 SELECT DATEADD(YEAR, 1, @now) --2017-07-21 14:39:46.4170000
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SELECT DATEADD(QUARTER, 1, @now) --2016-10-21 14:39:46.4170000 SELECT DATEADD(WEEK, 1, @now) --2016-07-28 14:39:46.4170000 SELECT DATEADD(DAY, 1, @now) --2016-07-22 14:39:46.4170000 SELECT DATEADD(HOUR, 1, @now) --2016-07-21 15:39:46.4170000 SELECT DATEADD(MINUTE, 1, @now) --2016-07-21 14:40:46.4170000 SELECT DATEADD(SECOND, 1, @now) --2016-07-21 14:39:47.4170000 SELECT DATEADD(MILLISECOND, 1, @now)--2016-07-21 14:39:46.4180000
NOTE: DATEADD also accepts abbreviations in the datepart parameter. Use of these abbreviations is generally discouraged as they can be confusing (m vs mi, ww vs w, etc.).
Section 9.4: Create function to calculate a person's age on a specific date
This function will take 2 datetime parameters, the DOB, and a date to check the age at
CREATE FUNCTION [dbo].[Calc_Age]
( @DOB datetime , @calcDate datetime ) RETURNS int AS BEGIN declare @age int
IF (@calcDate < @DOB ) RETURN -1
-- If a DOB is supplied after the comparison date, then return -1 SELECT @age = YEAR(@calcDate) - YEAR(@DOB) +
CASE WHEN DATEADD(year,YEAR(@calcDate) - YEAR(@DOB) ,@DOB) > @calcDate THEN -1 ELSE 0 END
RETURN @age
END
eg to check the age today of someone born on 1/1/2000
SELECT dbo.Calc_Age('2000-01-01',Getdate())
Section 9.5: Get the current DateTime
The built-in functions GETDATE and GETUTCDATE each return the current date and time without a time zone offset.
The return value of both functions is based on the operating system of the computer on which the instance of SQL Server is running.
The return value of GETDATE represents the current time in the same timezone as operating system. The return value of GETUTCDATE represents the current UTC time.
Either function can be included in the SELECT clause of a query or as part of boolean expression in the WHERE clause.
Examples:
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-- example query that selects the current time in both the server time zone and UTC SELECT GETDATE() as SystemDateTime, GETUTCDATE() as UTCDateTime
-- example query records with EventDate in the past. SELECT * FROM MyEvents WHERE EventDate < GETDATE()
There are a few other built-in functions that return different variations of the current date-time:
SELECT
GETDATE(), --2016-07-21 14:27:37.447 GETUTCDATE(), --2016-07-21 18:27:37.447 CURRENT_TIMESTAMP, --2016-07-21 14:27:37.447 SYSDATETIME(), --2016-07-21 14:27:37.4485768 SYSDATETIMEOFFSET(),--2016-07-21 14:27:37.4485768 -04:00 SYSUTCDATETIME() --2016-07-21 18:27:37.4485768
Section 9.6: Getting the last day of a month
Using the DATEADD and DATEDIFF functions, it's possible to return the last date of a month.
SELECT DATEADD(d, -1, DATEADD(m, DATEDIFF(m, 0, '2016-09-23') + 1, 0)) -- 2016-09-30 00:00:00.000
Version ≥ SQL Server 2012
The EOMONTH function provides a more concise way to return the last date of a month, and has an optional parameter to offset the month.
SELECT EOMONTH('2016-07-21') --2016-07-31 SELECT EOMONTH('2016-07-21', 4) --2016-11-30 SELECT EOMONTH('2016-07-21', -5) --2016-02-29
Section 9.7: CROSS PLATFORM DATE OBJECT
Version ≥ SQL Server 2012
In Transact SQL , you may define an object as Date (or DateTime) using the [DATEFROMPARTS][1] (or [DATETIMEFROMPARTS][1]) function like following:
DECLARE @myDate DATE=DATEFROMPARTS(1988,11,28) DECLARE @someMoment DATETIME=DATEFROMPARTS(1988,11,28,10,30,50,123)
The parameters you provide are Year, Month, Day for the DATEFROMPARTS function and, for the DATETIMEFROMPARTS function you will need to provide year, month, day, hour, minutes, seconds and milliseconds.
These methods are useful and worth being used because using the plain string to build a date(or datetime) may fail depending on the host machine region, location or date format settings.
Section 9.8: Return just Date from a DateTime
There are many ways to return a Date from a DateTime object
SELECT CONVERT(Date, GETDATE()) 1. SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, GETDATE())) returns 2016-07-21 00:00:00.000 2. SELECT CAST(GETDATE() AS DATE) 3. SELECT CONVERT(CHAR(10),GETDATE(),111) 4.
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SELECT FORMAT(GETDATE(), 'yyyy-MM-dd') 5.
Note that options 4 and 5 returns a string, not a date.
Section 9.9: DATEDIFF for calculating time period dierences
General syntax:
DATEDIFF (datepart, datetime_expr1, datetime_expr2)
It will return a positive number if datetime_expr is in the past relative to datetime_expr2, and a negative number otherwise.
Examples
DECLARE @now DATETIME2 = GETDATE(); DECLARE @oneYearAgo DATETIME2 = DATEADD(YEAR, -1, @now); SELECT @now --2016-07-21 14:49:50.9800000 SELECT @oneYearAgo --2015-07-21 14:49:50.9800000 SELECT DATEDIFF(YEAR, @oneYearAgo, @now) --1 SELECT DATEDIFF(QUARTER, @oneYearAgo, @now) --4 SELECT DATEDIFF(WEEK, @oneYearAgo, @now) --52 SELECT DATEDIFF(DAY, @oneYearAgo, @now) --366 SELECT DATEDIFF(HOUR, @oneYearAgo, @now) --8784 SELECT DATEDIFF(MINUTE, @oneYearAgo, @now) --527040 SELECT DATEDIFF(SECOND, @oneYearAgo, @now) --31622400
NOTE: DATEDIFF also accepts abbreviations in the datepart parameter. Use of these abbreviations is generally discouraged as they can be confusing (m vs mi, ww vs w, etc.).
DATEDIFF can also be used to determine the offset between UTC and the local time of the SQL Server. The following statement can be used to calculate the offset between UTC and local time (including timezone).
select DATEDIFF(hh, getutcdate(), getdate()) as 'CentralTimeOffset'
Section 9.10: DATEPART & DATENAME
DATEPART returns the specified datepart of the specified datetime expression as a numeric value.
DATENAME returns a character string that represents the specified datepart of the specified date. In practice DATENAME is mostly useful for getting the name of the month or the day of the week.
There are also some shorthand functions to get the year, month or day of a datetime expression, which behave like DATEPART with their respective datepart units.
Syntax:
DATEPART ( datepart , datetime_expr ) DATENAME ( datepart , datetime_expr ) DAY ( datetime_expr ) MONTH ( datetime_expr ) YEAR ( datetime_expr )
Examples:
DECLARE @now DATETIME2 = GETDATE();
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SELECT @now --2016-07-21 15:05:33.8370000 SELECT DATEPART(YEAR, @now) --2016 SELECT DATEPART(QUARTER, @now) --3 SELECT DATEPART(WEEK, @now) --30 SELECT DATEPART(HOUR, @now) --15 SELECT DATEPART(MINUTE, @now) --5 SELECT DATEPART(SECOND, @now) --33 -- Differences between DATEPART and DATENAME: SELECT DATEPART(MONTH, @now) --7 SELECT DATENAME(MONTH, @now) --July SELECT DATEPART(WEEKDAY, @now) --5 SELECT DATENAME(WEEKDAY, @now) --Thursday --shorthand functions SELECT DAY(@now) --21 SELECT MONTH(@now) --7 SELECT YEAR(@now) --2016
NOTE: DATEPART and DATENAME also accept abbreviations in the datepart parameter. Use of these abbreviations is generally discouraged as they can be confusing (m vs mi, ww vs w, etc.).
Section 9.11: Date parts reference
These are the datepart values available to date & time functions:
datepart Abbreviations year yy, yyyy
quarter qq, q month mm, m
dayofyear dy, y
day dd, d
week wk, ww
weekday dw, w hour hh
minute mi, n
second ss, s
millisecond ms
microsecond mcs nanosecond ns
NOTE: Use of abbreviations is generally discouraged as they can be confusing (m vs mi, ww vs w, etc.). The long version of the datepart representation promotes clarity and readability, and should be used whenever possible (month, minute, week, weekday, etc.).
Section 9.12: Date Format Extended
Date Format SQL Statement
Sample Output
YY-MM-DD
SELECT SELECT RIGHT(CONVERT(VARCHAR(10), REPLACE(CONVERT(VARCHAR(8), SYSDATETIME(), SYSDATETIME(), 20), 11), 8) '/', AS '-') [YY-MM-DD]
AS [YY-MM-DD]
11-06-08
YYYY-MM-DD
SELECT CONVERT(VARCHAR(10), SYSDATETIME(), 120) AS [YYYY-MM-DD] SELECT REPLACE(CONVERT(VARCHAR(10), SYSDATETIME(), 111), '/', '-') AS [YYYY- MM-DD]
2011-06-08
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SELECT CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) + '-' + YYYY-M-D
CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(DAY(SYSDATETIME()) AS
2011-6-8 VARCHAR(2)) AS [YYYY-M-D]
YY-M-D
SELECT RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) + '-' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) AS [YY-M-D]
11-6-8
M-D-YYYY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) AS [M-D-YYYY]
6-8-2011
M-D-YY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '-' + RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) AS [M-D-YY]
6-8-11
D-M-YYYY
SELECT CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) AS [D-M-YYYY]
8-6-2011
D-M-YY
SELECT CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '-' + RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) AS [D-M-YY]
8-6-11
YY-MM
SELECT RIGHT(CONVERT(VARCHAR(7), SYSDATETIME(), 20), 5) AS [YY-MM] SELECT SUBSTRING(CONVERT(VARCHAR(10), SYSDATETIME(), 120), 3, 5) AS [YY- MM]
11-06
YYYY-MM SELECT CONVERT(VARCHAR(7), SYSDATETIME(), 120) AS [YYYY-MM] 2011-06
YY-M
SELECT RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) + '-' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) AS [YY-M]
11-6
YYYY-M
SELECT CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) + '-' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) AS [YYYY-M]
2011-6
MM-YY
SELECT RIGHT(CONVERT(VARCHAR(8), SYSDATETIME(), 5), 5) AS [MM-YY] SELECT SUBSTRING(CONVERT(VARCHAR(8), SYSDATETIME(), 5), 4, 5) AS [MM-YY]
06-11
MM-YYYY SELECT RIGHT(CONVERT(VARCHAR(10), SYSDATETIME(), 105), 7) AS [MM-YYYY] 06-2011
M-YY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '-' + RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) AS [M-YY]
6-11
M-YYYY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) AS [M-YYYY]
6-2011
MM-DD SELECT CONVERT(VARCHAR(5), SYSDATETIME(), 10) AS [MM-DD] 06-08
DD-MM SELECT CONVERT(VARCHAR(5), SYSDATETIME(), 5) AS [DD-MM] 08-06
M-D
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) AS [M-D]
6-8
D-M
SELECT CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '-' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) AS [D-M]
8-6
M/D/YYYY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) AS [M/D/YYYY]
6/8/2011
M/D/YY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '/' + RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) AS [M/D/YY]
6/8/11
D/M/YYYY
SELECT CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) AS [D/M/YYYY]
8/6/2011
D/M/YY
SELECT CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '/' + RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) AS [D/M/YY]
8/6/11
YYYY/M/D
SELECT CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) + '/' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) AS [YYYY/M/D]
2011/6/8
GoalKicker.com – Microsoft® SQL Server® Notes for Professionals 36
SELECT RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) + '/' + YY/M/D
CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(DAY(SYSDATETIME()) AS
11/6/8 VARCHAR(2)) AS [YY/M/D]
MM/YY SELECT RIGHT(CONVERT(VARCHAR(8), SYSDATETIME(), 3), 5) AS [MM/YY] 06/11 MM/YYYY SELECT RIGHT(CONVERT(VARCHAR(10), SYSDATETIME(), 103), 7) AS [MM/YYYY] 06/2011
M/YY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '/' + RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) AS [M/YY]
6/11
M/YYYY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) AS [M/YYYY]
6/2011
YY/MM SELECT CONVERT(VARCHAR(5), SYSDATETIME(), 11) AS [YY/MM] 11/06
YYYY/MM SELECT CONVERT(VARCHAR(7), SYSDATETIME(), 111) AS [YYYY/MM] 2011/06
YY/M
SELECT RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) + '/' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) AS [YY/M]
11/6
YYYY/M
SELECT CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) + '/' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) AS [YYYY/M]
2011/6
MM/DD SELECT CONVERT(VARCHAR(5), SYSDATETIME(), 1) AS [MM/DD] 06/08
DD/MM SELECT CONVERT(VARCHAR(5), SYSDATETIME(), 3) AS [DD/MM] 08/06
M/D
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) AS [M/D]
6/8
D/M
SELECT CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '/' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) AS [D/M]
8/6
MM.DD.YYYY
SELECT REPLACE(CONVERT(VARCHAR(10), SYSDATETIME(), 101), '/', '.') AS [MM.DD.YYYY]
06.08.2011
MM.DD.YY SELECT REPLACE(CONVERT(VARCHAR(8), SYSDATETIME(), 1), '/', '.') AS [MM.DD.YY] 06.08.11
M.D.YYYY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '.' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '.' + CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) AS [M.D.YYYY]
6.8.2011
M.D.YY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '.' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '.' + RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) AS [M.D.YY]
6.8.11
DD.MM.YYYY SELECT CONVERT(VARCHAR(10), SYSDATETIME(), 104) AS [DD.MM.YYYY] 08.06.2011
DD.MM.YY SELECT CONVERT(VARCHAR(10), SYSDATETIME(), 4) AS [DD.MM.YY] 08.06.11
D.M.YYYY
SELECT CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '.' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '.' + CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) AS [D.M.YYYY]
8.6.2011
D.M.YY
SELECT CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + '.' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '.' + RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) AS [D.M.YY]
8.6.11
YYYY.M.D
SELECT CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) + '.' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '.' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) AS [YYYY.M.D]
2011.6.8
YY.M.D
SELECT RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) + '.' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '.' + CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) AS [YY.M.D]
11.6.8
MM.YYYY SELECT RIGHT(CONVERT(VARCHAR(10), SYSDATETIME(), 104), 7) AS [MM.YYYY] 06.2011
MM.YY SELECT RIGHT(CONVERT(VARCHAR(8), SYSDATETIME(), 4), 5) AS [MM.YY] 06.11
M.YYYY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '.' + CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) AS [M.YYYY]
6.2011
M.YY
SELECT CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) + '.' + RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) AS [M.YY]
6.11
YYYY.MM SELECT CONVERT(VARCHAR(7), SYSDATETIME(), 102) AS [YYYY.MM] 2011.06
YY.MM SELECT CONVERT(VARCHAR(5), SYSDATETIME(), 2) AS [YY.MM] 11.06
GoalKicker.com – Microsoft® SQL Server® Notes for Professionals 37
SELECT YYYY.M
CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)) + '.' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) AS [YYYY.M]
2011.6
YY.M
SELECT RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) + '.' + CAST(MONTH(SYSDATETIME()) AS VARCHAR(2)) AS [YY.M]
11.6
MM.DD SELECT RIGHT(CONVERT(VARCHAR(8), SYSDATETIME(), 2), 5) AS [MM.DD] 06.08
DD.MM SELECT CONVERT(VARCHAR(5), SYSDATETIME(), 4) AS [DD.MM] 08.06
MMDDYYYY
SELECT REPLACE(CONVERT(VARCHAR(10), SYSDATETIME(), 101), '/', '') AS [MMDDYYYY]
06082011
MMDDYY SELECT REPLACE(CONVERT(VARCHAR(8), SYSDATETIME(), 1), '/', '') AS [MMDDYY] 060811
DDMMYYYY
SELECT REPLACE(CONVERT(VARCHAR(10), SYSDATETIME(), 103), '/', '') AS [DDMMYYYY]
08062011
DDMMYY SELECT REPLACE(CONVERT(VARCHAR(8), SYSDATETIME(), 3), '/', '') AS [DDMMYY] 080611
MMYYYY
SELECT RIGHT(REPLACE(CONVERT(VARCHAR(10), SYSDATETIME(), 103), '/', ''), 6) AS [MMYYYY]
062011
MMYY
SELECT [MMYY]
RIGHT(REPLACE(CONVERT(VARCHAR(8), SYSDATETIME(), 3), '/', ''), 4) AS
0611
YYYYMM SELECT CONVERT(VARCHAR(6), SYSDATETIME(), 112) AS [YYYYMM] 201106
YYMM SELECT CONVERT(VARCHAR(4), SYSDATETIME(), 12) AS [YYMM] 1106
Month DD, YYYY
SELECT DATENAME(MONTH, SYSDATETIME())+ ' ' + RIGHT('0' + DATENAME(DAY, SYSDATETIME()), 2) + ', ' + DATENAME(YEAR, SYSDATETIME()) AS [Month DD, YYYY]
June 08, 2011
Mon YYYY
SELECT LEFT(DATENAME(MONTH, SYSDATETIME()), 3) + ' ' + DATENAME(YEAR, SYSDATETIME()) AS [Mon YYYY]
Jun 2011
Month YYYY
SELECT DATENAME(MONTH, SYSDATETIME()) + ' ' + DATENAME(YEAR, SYSDATETIME()) AS [Month YYYY]
June 2011
DD Month
SELECT RIGHT('0' + DATENAME(DAY, SYSDATETIME()) AS [DD Month]
SYSDATETIME()), 2) + ' ' + DATENAME(MONTH,
08 June
Month DD
SELECT DATENAME(MONTH, SYSDATETIME()) SYSDATETIME()), 2) AS [Month DD]
+ ' ' + RIGHT('0' + DATENAME(DAY,
June 08
DD Month YY
SELECT CAST(DAY(SYSDATETIME()) AS VARCHAR(2)) + ' ' + DATENAME(MM, SYSDATETIME()) + ' ' + RIGHT(CAST(YEAR(SYSDATETIME()) AS VARCHAR(4)), 2) AS [DD Month YY]
08 June 11
DD Month YYYY
SELECT RIGHT('0' + DATENAME(DAY, SYSDATETIME()), 2) + ' ' + DATENAME(MONTH, SYSDATETIME())+ ' ' + DATENAME(YEAR, SYSDATETIME()) AS [DD Month YYYY]
08 June 2011
Mon-YY
SELECT REPLACE(RIGHT(CONVERT(VARCHAR(9), SYSDATETIME(), 6), 6), ' ', '-') AS [Mon-YY]
Jun-08
Mon-YYYY
SELECT REPLACE(RIGHT(CONVERT(VARCHAR(11), SYSDATETIME(), 106), 8), ' ', '-') AS [Mon-YYYY]
Jun-2011
DD-Mon-YY SELECT REPLACE(CONVERT(VARCHAR(9), SYSDATETIME(), 6), ' ', '-') AS [DD-Mon-YY] 08-Jun-11
DD-Mon-YYYY
SELECT YYYY]
REPLACE(CONVERT(VARCHAR(11), SYSDATETIME(), 106), ' ', '-') AS [DD-Mon-
08-Jun-2011
GoalKicker.com – Microsoft® SQL Server® Notes for Professionals 38
Chapter 10: Generating a range of dates
Parameter Details @FromDate The inclusive lower boundary of the generated date range.
@ToDate The inclusive upper boundary of the generated date range.
Section 10.1: Generating Date Range With Recursive CTE
Using a Recursive CTE, you can generate an inclusive range of dates:
Declare @FromDate Date = '2014-04-21',
@ToDate Date = '2014-05-02'
;With DateCte (Date) As (
Select @FromDate Union All Select DateAdd(Day, 1, Date) From DateCte Where Date < @ToDate ) Select Date From DateCte Option (MaxRecursion 0)
The default MaxRecursion setting is 100. Generating more than 100 dates using this method will require the Option (MaxRecursion N) segment of the query, where N is the desired MaxRecursion setting. Setting this to 0 will remove the MaxRecursion limitation altogether.
Section 10.2: Generating a Date Range With a Tally Table
Another way you can generate a range of dates is by utilizing a Tally Table to create the dates between the range:
Declare @FromDate Date = '2014-04-21',
@ToDate Date = '2014-05-02'
;With
E1(N) As (Select 1 From (Values (1), (1), (1), (1), (1), (1), (1), (1), (1), (1)) DT(N)), E2(N) As (Select 1 From E1 A Cross Join E1 B), E4(N) As (Select 1 From E2 A Cross Join E2 B), E6(N) As (Select 1 From E4 A Cross Join E2 B), Tally(N) As (
Select Row_Number() Over (Order By (Select Null)) From E6 ) Select DateAdd(Day, N - 1, @FromDate) Date From Tally Where N <= DateDiff(Day, @FromDate, @ToDate) + 1
GoalKicker.com – Microsoft® SQL Server® Notes for Professionals 39
Chapter 11: Database Snapshots
Section 11.1: Create a database snapshot
A database snapshot is a read-only, static view of a SQL Server database (the source database). It is similar to backup, but it is available as any other database so client can query snapshot database.
CREATE DATABASE MyDatabase_morning -- name of the snapshot ON (
NAME=MyDatabase_data, -- logical name of the data file of the source database FILENAME='C:\SnapShots\MySnapshot_Data.ss' -- snapshot file; ) AS SNAPSHOT OF MyDatabase; -- name of source database
You can also create snapshot of database with multiple files:
CREATE DATABASE MyMultiFileDBSnapshot ON
(NAME=MyMultiFileDb_ft, FILENAME='C:\SnapShots\MyMultiFileDb_ft.ss'), (NAME=MyMultiFileDb_sys, FILENAME='C:\SnapShots\MyMultiFileDb_sys.ss'), (NAME=MyMultiFileDb_data, FILENAME='C:\SnapShots\MyMultiFileDb_data.ss'), (NAME=MyMultiFileDb_indx, FILENAME='C:\SnapShots\MyMultiFileDb_indx.ss') AS SNAPSHOT OF MultiFileDb;
Section 11.2: Restore a database snapshot
If data in a source database becomes damaged or some wrong data is written into database, in some cases, reverting the database to a database snapshot that predates the damage might be an appropriate alternative to restoring the database from a backup.
RESTORE DATABASE MYDATABASE FROM DATABASE_SNAPSHOT='MyDatabase_morning';
Warning: This will delete all changes made to the source database since the snapshot was taken!
Section 11.3: DELETE Snapshot
You can delete existing snapshots of database using DELETE DATABASE statement:
DROP DATABASE Mydatabase_morning
In this statement you should reference name of the database snapshot.
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Chapter 12: COALESCE
Section 12.1: Using COALESCE to Build Comma-Delimited String
We can get a comma delimited string from multiple rows using coalesce as shown below.
Since table variable is used, we need to execute whole query once. So to make easy to understand, I have added BEGIN and END block.
BEGIN
--Table variable declaration to store sample records DECLARE @Table TABLE (FirstName varchar(256), LastName varchar(256))
--Inserting sample records into table variable @Table INSERT INTO @Table (FirstName, LastName) VALUES ('John','Smith'), ('Jane','Doe')
--Creating variable to store result DECLARE @Names varchar(4000)
--Used COLESCE function, so it will concatenate comma separated FirstName into @Names varible SELECT @Names = COALESCE(@Names + ',', '') + FirstName FROM @Table
--Now selecting actual result SELECT @Names END
Section 12.2: Getting the first not null from a list of column values
SELECT COALESCE(NULL, NULL, 'TechOnTheNet.com', NULL, 'CheckYourMath.com'); Result: 'TechOnTheNet.com'
SELECT COALESCE(NULL, 'TechOnTheNet.com', 'CheckYourMath.com'); Result: 'TechOnTheNet.com'
SELECT COALESCE(NULL, NULL, 1, 2, 3, NULL, 4); Result: 1
Section 12.3: Coalesce basic Example
COALESCE() returns the first NON NULL value in a list of arguments. Suppose we had a table containing phone numbers, and cell phone numbers and wanted to return only one for each user. In order to only obtain one, we can get the first NON NULL value.
DECLARE @Table TABLE (UserID int, PhoneNumber varchar(12), CellNumber varchar(12)) INSERT INTO @Table (UserID, PhoneNumber, CellNumber) VALUES (1,'555-869-1123',NULL), (2,'555-123-7415','555-846-7786'), (3,NULL,'555-456-8521')
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SELECT
UserID, COALESCE(PhoneNumber, CellNumber) FROM
@Table
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Chapter 13: IF...ELSE
Section 13.1: Single IF statement
Like most of the other programming languages, T-SQL also supports IF..ELSE statements.
For example in the example below 1 = 1 is the expression, which evaluates to True and the control enters the BEGIN..END block and the Print statement prints the string 'One is equal to One'
IF ( 1 = 1) --<-- Some Expression
BEGIN
PRINT 'One is equal to One' END
Section 13.2: Multiple IF Statements
We can use multiple IF statement to check multiple expressions totally independent from each other.
In the example below, each IF statement's expression is evaluated and if it is true the code inside the BEGIN...END block is executed. In this particular example, the First and Third expressions are true and only those print statements will be executed.
IF (1 = 1) --<-- Some Expression --<-- This is true BEGIN
PRINT 'First IF is True' --<-- this will be executed END
IF (1 = 2) --<-- Some Expression BEGIN
PRINT 'Second IF is True' END
IF (3 = 3) --<-- Some Expression --<-- This true BEGIN
PRINT 'Thrid IF is True' --<-- this will be executed END
Section 13.3: Single IF..ELSE statement
In a single IF..ELSE statement, if the expression evaluates to True in the IF statement the control enters the first BEGIN..END block and only the code inside that block gets executed , Else block is simply ignored.
On the other hand if the expression evaluates to False the ELSE BEGIN..END block gets executed and the control never enters the first BEGIN..END Block.
In the Example below the expression will evaluate to false and the Else block will be executed printing the string 'First expression was not true'
IF ( 1 <> 1) --<-- Some Expression
BEGIN
PRINT 'One is equal to One' END ELSE
BEGIN
PRINT 'First expression was not true'
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END
Section 13.4: Multiple IF... ELSE with final ELSE Statements
If we have Multiple IF...ELSE IF statements but we also want also want to execute some piece of code if none of expressions are evaluated to True , then we can simple add a final ELSE block which only gets executed if none of the IF or ELSE IF expressions are evaluated to true.
In the example below none of the IF or ELSE IF expression are True hence only ELSE block is executed and prints 'No other expression is true'
IF ( 1 = 1 + 1 )
BEGIN
PRINT 'First If Condition' END ELSE IF (1 = 2)
BEGIN
PRINT 'Second If Else Block' END ELSE IF (1 = 3)
BEGIN
PRINT 'Third If Else Block' END ELSE
BEGIN
PRINT 'No other expression is true' --<-- Only this statement will be printed END
Section 13.5: Multiple IF...ELSE Statements
More often than not we need to check multiple expressions and take specific actions based on those expressions. This situation is handled using multiple IF...ELSE IF statements.
In this example all the expressions are evaluated from top to bottom. As soon as an expression evaluates to true, the code inside that block is executed. If no expression is evaluated to true, nothing gets executed.
IF (1 = 1 + 1) BEGIN
PRINT 'First If Condition' END ELSE IF (1 = 2) BEGIN
PRINT 'Second If Else Block' END ELSE IF (1 = 3) BEGIN
PRINT 'Third If Else Block' END ELSE IF (1 = 1) --<-- This is True BEGIN
PRINT 'Last Else Block' --<-- Only this statement will be printed END
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Chapter 14: CASE Statement
Section 14.1: Simple CASE statement
In a simple case statement, one value or variable is checked against multiple possible answers. The code below is an example of a simple case statement:
SELECT CASE DATEPART(WEEKDAY, GETDATE())
WHEN 1 THEN 'Sunday' WHEN 2 THEN 'Monday' WHEN 3 THEN 'Tuesday' WHEN 4 THEN 'Wednesday' WHEN 5 THEN 'Thursday' WHEN 6 THEN 'Friday' WHEN 7 THEN 'Saturday' END
Section 14.2: Searched CASE statement
In a Searched Case statement, each option can test one or more values independently. The code below is an example of a searched case statement:
DECLARE @FirstName varchar(30) = 'John' DECLARE @LastName varchar(30) = 'Smith'
SELECT CASE
WHEN LEFT(@FirstName, 1) IN ('a','e','i','o','u')
THEN 'First name starts with a vowel' WHEN LEFT(@LastName, 1) IN ('a','e','i','o','u')
THEN 'Last name starts with a vowel' ELSE
'Neither name starts with a vowel' END
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Chapter 15: INSERT INTO
The INSERT INTO statement is used to insert new records in a table.
Section 15.1: INSERT multiple rows of data
To insert multiple rows of data in SQL Server 2008 or later:
INSERT INTO USERS VALUES (2, 'Michael', 'Blythe'), (3, 'Linda', 'Mitchell'), (4, 'Jillian', 'Carson'), (5, 'Garrett', 'Vargas');
To insert multiple rows of data in earlier versions of SQL Server, use "UNION ALL" like so:
INSERT INTO USERS (FIRST_NAME, LAST_NAME) SELECT 'James', 'Bond' UNION ALL SELECT 'Miss', 'Moneypenny' UNION ALL SELECT 'Raoul', 'Silva'
Note, the "INTO" keyword is optional in INSERT queries. Another warning is that SQL server only supports 1000 rows in one INSERT so you have to split them in batches.
Section 15.2: Use OUTPUT to get the new Id
When INSERTing, you can use OUTPUT INSERTED.ColumnName to get values from the newly inserted row, for example the newly generated Id - useful if you have an IDENTITY column or any sort of default or calculated value.
When programmatically calling this (e.g., from ADO.net) you would treat it as a normal query and read the values as if you would've made a SELECT-statement.
-- CREATE TABLE OutputTest ([Id] INT NOT NULL PRIMARY KEY IDENTITY, [Name] NVARCHAR(50))
INSERT INTO OutputTest ([Name]) OUTPUT INSERTED.[Id] VALUES ('Testing')
If the ID of the recently added row is required inside the same set of query or stored procedure.
-- CREATE a table variable having column with the same datatype of the ID
DECLARE @LastId TABLE ( id int);
INSERT INTO OutputTest ([Name]) OUTPUT INSERTED.[Id] INTO @LastId VALUES ('Testing')
SELECT id FROM @LastId
-- We can set the value in a variable and use later in procedure
DECLARE @LatestId int = (SELECT id FROM @LastId)
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Section 15.3: INSERT from SELECT Query Results
To insert data retrieved from SQL query (single or multiple rows)
INSERT INTO Table_name (FirstName, LastName, Position) SELECT FirstName, LastName, 'student' FROM Another_table_name
Note, 'student' in SELECT is a string constant that will be inserted in each row.
If required, you can select and insert data from/into the same table
Section 15.4: INSERT a single row of data
A single row of data can be inserted in two ways:
INSERT INTO USERS(Id, FirstName, LastName) VALUES (1, 'Mike', 'Jones');
Or
INSERT INTO USERS VALUES (1, 'Mike', 'Jones');
Note that the second insert statement only allows the values in exactly the same order as the table columns whereas in the first insert, the order of the values can be changed like:
INSERT INTO USERS(FirstName, LastName, Id) VALUES ('Mike', 'Jones', 1);
Section 15.5: INSERT on specific columns
To do an insert on specific columns (as opposed to all of them) you must specify the columns you want to update.
INSERT INTO USERS (FIRST_NAME, LAST_NAME) VALUES ('Stephen', 'Jiang');
This will only work if the columns that you did not list are nullable, identity, timestamp data type or computed columns; or columns that have a default value constraint. Therefore, if any of them are non-nullable, non-identity, non-timestamp, non-computed, non-default valued columns...then attempting this kind of insert will trigger an error message telling you that you have to provide a value for the applicable field(s).
Section 15.6: INSERT Hello World INTO table
CREATE TABLE MyTableName (
Id INT, MyColumnName NVARCHAR(1000) ) GO
INSERT INTO MyTableName (Id, MyColumnName) VALUES (1, N'Hello World!') GO
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Chapter 16: MERGE
Starting with SQL Server 2008, it is possible to perform insert, update, or delete operations in a single statement using the MERGE statement.
The MERGE statement allows you to join a data source with a target table or view, and then perform multiple actions against the target based on the results of that join.
Section 16.1: MERGE to Insert / Update / Delete
MERGE INTO targetTable
USING sourceTable ON (targetTable.PKID = sourceTable.PKID)
WHEN MATCHED AND (targetTable.PKID > 100) THEN
DELETE
WHEN MATCHED AND (targetTable.PKID <= 100) THEN
UPDATE SET
targetTable.ColumnA = sourceTable.ColumnA, targetTable.ColumnB = sourceTable.ColumnB
WHEN NOT MATCHED THEN
INSERT (ColumnA, ColumnB) VALUES (sourceTable.ColumnA, sourceTable.ColumnB);
WHEN NOT MATCHED BY SOURCE THEN
DELETE ; --< Required
Description:
MERGE INTO targetTable - table to be modified USING sourceTable - source of data (can be table or view or table valued function) ON ... - join condition between targetTable and sourceTable. WHEN MATCHED - actions to take when a match is found
AND (targetTable.PKID > 100) - additional condition(s) that must be satisfied in order for the action to be taken THEN DELETE - delete matched record from the targetTable THEN UPDATE - update columns of matched record specified by SET .... WHEN NOT MATCHED - actions to take when match is not found in targetTable WHEN NOT MATCHED BY SOURCE - actions to take when match is not found in sourceTable
Comments:
If a specific action is not needed then omit the condition e.g. removing WHEN NOT MATCHED THEN INSERT will prevent records from being inserted
Merge statement requires a terminating semicolon.
Restrictions:
WHEN MATCHED does not allow INSERT action UPDATE action can update a row only once. This implies that the join condition must produce unique matches.
GoalKicker.com – Microsoft® SQL Server® Notes for Professionals 48
Section 16.2: Merge Using CTE Source
WITH SourceTableCTE AS (
SELECT * FROM SourceTable ) MERGE
TargetTable AS target USING SourceTableCTE AS source ON (target.PKID = source.PKID) WHEN MATCHED THEN
UPDATE SET target.ColumnA = source.ColumnA WHEN NOT MATCHED THEN
INSERT (ColumnA) VALUES (Source.ColumnA);
Section 16.3: Merge Example - Synchronize Source And Target Table
To Illustrate the MERGE Statement, consider the following two tables -
dbo.Product : This table contains information about the product that company is currently selling 1.
dbo.ProductNew: This table contains information about the product that the company will sell in the future. 2.
The following T-SQL will create and populate these two tables
IF OBJECT_id(N'dbo.Product',N'U') IS NOT NULL DROP TABLE dbo.Product GO
CREATE TABLE dbo.Product ( ProductID INT PRIMARY KEY, ProductName NVARCHAR(64), PRICE MONEY )
IF OBJECT_id(N'dbo.ProductNew',N'U') IS NOT NULL DROP TABLE dbo.ProductNew GO
CREATE TABLE dbo.ProductNew ( ProductID INT PRIMARY KEY, ProductName NVARCHAR(64), PRICE MONEY )
INSERT INTO dbo.Product VALUES(1,'IPod',300) ,(2,'IPhone',400) ,(3,'ChromeCast',100) ,(4,'raspberry pi',50)
INSERT INTO dbo.ProductNew VALUES(1,'Asus Notebook',300) ,(2,'Hp Notebook',400) ,(3,'Dell Notebook',100) ,(4,'raspberry pi',50)
Now, Suppose we want to synchoronize the dbo.Product Target Table with the dbo.ProductNew table. Here is the criterion for this task:
GoalKicker.com – Microsoft® SQL Server® Notes for Professionals 49
Product that exist in both the dbo.ProductNew source table and the dbo.Product target table are updated in 1.
the dbo.Product target table with new new Products.
Any product in the dbo.ProductNew source table that do not exist in the dob.Product target table are 2.
inserted into the dbo.Product target table.
Any Product in the dbo.Product target table that do not exist in the dbo.ProductNew source table must be 3.
deleted from the dbo.Product target table. Here is the MERGE statement to perform this task.
MERGE dbo.Product AS SourceTbl USING dbo.ProductNew AS TargetTbl ON (SourceTbl.ProductID = TargetTbl.ProductID) WHEN MATCHED
AND SourceTbl.ProductName <> TargetTbl.ProductName OR SourceTbl.Price <> TargetTbl.Price THEN UPDATE SET SourceTbl.ProductName = TargetTbl.ProductName,
SourceTbl.Price = TargetTbl.Price WHEN NOT MATCHED
THEN INSERT (ProductID, ProductName, Price)
VALUES (TargetTbl.ProductID, TargetTbl.ProductName, TargetTbl.Price) WHEN NOT MATCHED BY SOURCE
THEN DELETE OUTPUT $action, INSERTED.*, DELETED.*;
Note:Semicolon must be present in the end of MERGE statement.
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Section 16.4: MERGE using Derived Source Table
MERGE INTO TargetTable AS Target USING (VALUES (1,'Value1'), (2, 'Value2'), (3,'Value3'))
AS Source (PKID, ColumnA) ON Target.PKID = Source.PKID WHEN MATCHED THEN
UPDATE SET target.ColumnA= source.ColumnA WHEN NOT MATCHED THEN
INSERT (PKID, ColumnA) VALUES (Source.PKID, Source.ColumnA);
Section 16.5: Merge using EXCEPT
Use EXCEPT to prevent updates to unchanged records
MERGE TargetTable targ USING SourceTable AS src
ON src.id = targ.id WHEN MATCHED
AND EXISTS (
SELECT src.field EXCEPT SELECT targ.field ) THEN
UPDATE SET field = src.field WHEN NOT MATCHED BY TARGET
THEN
INSERT (
id ,field ) VALUES (
src.id ,src.field ) WHEN NOT MATCHED BY SOURCE
THEN
DELETE;
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Chapter 17: CREATE VIEW
Section 17.1: CREATE Indexed VIEW
To create a view with an index, the view must be created using the WITH SCHEMABINDING keywords:
CREATE VIEW view_EmployeeInfo WITH SCHEMABINDING AS
SELECT EmployeeID, FirstName, LastName, HireDate FROM [dbo].Employee GO
Any clustered or non-clustered indexes can be now be created:
CREATE UNIQUE CLUSTERED INDEX IX_view_EmployeeInfo ON view_EmployeeInfo (
EmployeeID ASC )
There Are some limitations to indexed Views:
The view definition can reference one or more tables in the same database.
Once the unique clustered index is created, additional nonclustered indexes can be created against the view.
You can update the data in the underlying tables – including inserts, updates, deletes, and even truncates.
You can’t modify the underlying tables and columns. The view is created with the WITH SCHEMABINDING option.
It can’t contain COUNT, MIN, MAX, TOP, outer joins, or a few other keywords or elements.
For more information about creating indexed Views you can read this MSDN article
Section 17.2: CREATE VIEW
CREATE VIEW view_EmployeeInfo AS
SELECT EmployeeID, FirstName, LastName, HireDate FROM Employee GO
Rows from views can be selected much like tables:
SELECT FirstName FROM view_EmployeeInfo
You may also create a view with a calculated column. We can modify the view above as follows by adding a
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calculated column:
CREATE VIEW view_EmployeeReport AS
SELECT EmployeeID, FirstName, LastName, Coalesce(FirstName,'') + ' ' + Coalesce(LastName,'') as FullName, HireDate FROM Employee GO
This view adds an additional column that will appear when you SELECT rows from it. The values in this additional column will be dependent on the fields FirstName and LastName in the table Employee and will automatically update behind-the-scenes when those fields are updated.
Section 17.3: CREATE VIEW With Encryption
CREATE VIEW view_EmployeeInfo WITH ENCRYPTION AS SELECT EmployeeID, FirstName, LastName, HireDate FROM Employee GO
Section 17.4: CREATE VIEW With INNER JOIN
CREATE VIEW view_PersonEmployee AS
SELECT P.LastName,
P.FirstName, E.JobTitle FROM Employee AS E INNER JOIN Person AS P
ON P.BusinessEntityID = E.BusinessEntityID GO
Views can use joins to select data from numerous sources like tables, table functions, or even other views. This example uses the FirstName and LastName columns from the Person table and the JobTitle column from the Employee table.
This view can now be used to see all corresponding rows for Managers in the database:
SELECT * FROM view_PersonEmployee WHERE JobTitle LIKE '%Manager%'
Section 17.5: Grouped VIEWs
A grouped VIEW is based on a query with a GROUP BY clause. Since each of the groups may have more than one row in the base from which it was built, these are necessarily read-only VIEWs. Such VIEWs usually have one or more aggregate functions and they are used for reporting purposes. They are also handy for working around weaknesses in SQL. Consider a VIEW that shows the largest sale in each state. The query is straightforward:
https://www.simple-talk.com/sql/t-sql-programming/sql-view-beyond-the-basics/
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CREATE VIEW BigSales (state_code, sales_amt_total) AS SELECT state_code, MAX(sales_amt)
FROM Sales GROUP BY state_code;
Section 17.6: UNION-ed VIEWs
VIEWs based on a UNION or UNION ALL operation are read-only because there is no single way to map a change onto just one row in one of the base tables. The UNION operator will remove duplicate rows from the results. Both the UNION and UNION ALL operators hide which table the rows came from. Such VIEWs must use a , because the columns in a UNION [ALL] have no names of their own. In theory, a UNION of two disjoint tables, neither of which has duplicate rows in itself should be updatable.
https://www.simple-talk.com/sql/t-sql-programming/sql-view-beyond-the-basics/
CREATE VIEW DepTally2 (emp_nbr, dependent_cnt) AS (SELECT emp_nbr, COUNT(*)
FROM Dependents GROUP BY emp_nbr) UNION (SELECT emp_nbr, 0
FROM Personnel AS P2 WHERE NOT EXISTS
(SELECT *
FROM Dependents AS D2 WHERE D2.emp_nbr = P2.emp_nbr));
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Chapter 18: Views
Section 18.1: Create a view with schema binding
If a view is created WITH SCHEMABINDING, the underlying table(s) can't be dropped or modified in such a way that they would break the view. For example, a table column referenced in a view can't be removed.
CREATE VIEW dbo.PersonsView WITH SCHEMABINDING AS SELECT
name, address FROM dbo.PERSONS -- database schema must be specified when WITH SCHEMABINDING is present
Views without schema binding can break if their underlying table(s) change or get dropped. Querying a broken view results in an error message. sp_refreshview can be used to ensure existing views without schema binding aren't broken.
Section 18.2: Create a view
CREATE VIEW dbo.PersonsView AS SELECT
name, address FROM persons;
Section 18.3: Create or replace view
This query will drop the view - if it already exists - and create a new one.
IF OBJECT_ID('dbo.PersonsView', 'V') IS NOT NULL
DROP VIEW dbo.PersonsView GO
CREATE VIEW dbo.PersonsView AS SELECT
name, address FROM persons;
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Chapter 19: UNION
Section 19.1: Union and union all
Union operation combines the results of two or more queries into a single result set that includes all the rows that belong to all queries in the union and will ignore any duplicates that exist. Union all also does the same thing but include even the duplicate values. The concept of union operation will be clear from the example below. Few things to consider while using union are:
1.The number and the order of the columns must be the same in all queries.
2.The data types must be compatible.
Example:
We have three tables : Marksheet1, Marksheet2 and Marksheet3. Marksheet3 is the duplicate table of Marksheet2 which contains same values as that of Marksheet2.
Table1: Marksheet1
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Table2: Marksheet2
Table3: Marksheet3
Union on tables Marksheet1 and Marksheet2
SELECT SubjectCode, SubjectName, MarksObtained FROM Marksheet1 UNION SELECT CourseCode, CourseName, MarksObtained FROM Marksheet2
Note: The output for union of the three tables will also be same as union on Marksheet1 and Marksheet2 because union operation does not take duplicate values.
SELECT SubjectCode, SubjectName, MarksObtained FROM Marksheet1 UNION SELECT CourseCode, CourseName, MarksObtained FROM Marksheet2 UNION SELECT SubjectCode, SubjectName, MarksObtained FROM Marksheet3
OUTPUT
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Union All
SELECT SubjectCode, SubjectName, MarksObtained FROM Marksheet1 UNION ALL SELECT CourseCode, CourseName, MarksObtained FROM Marksheet2 UNION ALL SELECT SubjectCode, SubjectName, MarksObtained FROM Marksheet3
OUTPUT
You will notice here that the duplicate values from Marksheet3 are also displayed using union all.
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Chapter 20: TRY/CATCH
Section 20.1: Transaction in a TRY/CATCH
This will rollback both inserts due to an invalid datetime:
BEGIN TRANSACTION BEGIN TRY
INSERT INTO dbo.Sale(Price, SaleDate, Quantity) VALUES (5.2, GETDATE(), 1) INSERT INTO dbo.Sale(Price, SaleDate, Quantity) VALUES (5.2, 'not a date', 1) COMMIT TRANSACTION END TRY BEGIN CATCH
ROLLBACK TRANSACTION -- First Rollback and then throw. THROW END CATCH
This will commit both inserts:
BEGIN TRANSACTION BEGIN TRY
INSERT INTO dbo.Sale(Price, SaleDate, Quantity) VALUES (5.2, GETDATE(), 1) INSERT INTO dbo.Sale(Price, SaleDate, Quantity) VALUES (5.2, GETDATE(), 1) COMMIT TRANSACTION END TRY BEGIN CATCH
THROW ROLLBACK TRANSACTION END CATCH
Section 20.2: Raising errors in try-catch block
RAISERROR function will generate error in the TRY CATCH block:
DECLARE @msg nvarchar(50) = 'Here is a problem!' BEGIN TRY
print 'First statement'; RAISERROR(@msg, 11, 1); print 'Second statement'; END TRY BEGIN CATCH
print 'Error: ' + ERROR_MESSAGE(); END CATCH
RAISERROR with second parameter greater than 10 (11 in this example) will stop execution in TRY BLOCK and raise an error that will be handled in CATCH block. You can access error message using ERROR_MESSAGE() function. Output of this sample is:
First statement Error: Here is a problem!
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Section 20.3: Raising info messages in try catch block
RAISERROR with severity (second parameter) less or equal to 10 will not throw exception.
BEGIN TRY
print 'First statement'; RAISERROR( 'Here is a problem!', 10, 15); print 'Second statement'; END TRY BEGIN CATCH
print 'Error: ' + ERROR_MESSAGE(); END CATCH
After RAISERROR statement, third statement will be executed and CATCH block will not be invoked. Result of execution is:
First statement Here is a problem! Second statement
Section 20.4: Re-throwing exception generated by RAISERROR
You can re-throw error that you catch in CATCH block using TRHOW statement:
DECLARE @msg nvarchar(50) = 'Here is a problem! Area: ''%s'' Line:''%i''' BEGIN TRY
print 'First statement'; RAISERROR(@msg, 11, 1, 'TRY BLOCK', 2); print 'Second statement'; END TRY BEGIN CATCH
print 'Error: ' + ERROR_MESSAGE(); THROW; END CATCH
Note that in this case we are raising error with formatted arguments (fourth and fifth parameter). This might be useful if you want to add more info in message. Result of execution is:
First statement Error: Here is a problem! Area: 'TRY BLOCK' Line:'2' Msg 50000, Level 11, State 1, Line 26 Here is a problem! Area: 'TRY BLOCK' Line:'2'
Section 20.5: Throwing exception in TRY/CATCH blocks
You can throw exception in try catch block:
DECLARE @msg nvarchar(50) = 'Here is a problem!' BEGIN TRY
print 'First statement'; THROW 51000, @msg, 15; print 'Second statement'; END TRY BEGIN CATCH
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print 'Error: ' + ERROR_MESSAGE(); THROW; END CATCH
Exception with be handled in CATCH block and then re-thrown using THROW without parameters.
First statement Error: Here is a problem! Msg 51000, Level 16, State 15, Line 39 Here is a problem!
THROW is similar to RAISERROR with following differences:
Recommendation is that new applications should use THROW instead of RASIERROR. THROW can use any number as first argument (error number), RAISERROR can use only ids in sys.messages view THROW has severity 16 (cannot be changed) THROW cannot format arguments like RAISERROR. Use FORMATMESSAGE function as an argument of RAISERROR if you need this feature.
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Chapter 21: WHILE loop
Section 21.1: Using While loop
The WHILE loop can be used as an alternative to CURSORS. The following example will print numbers from 0 to 99.
DECLARE @i int = 0; WHILE(@i < 100) BEGIN
PRINT @i; SET @i = @i+1 END
Section 21.2: While loop with min aggregate function usage
DECLARE @ID AS INT;
SET @ID = (SELECT MIN(ID) from TABLE);
WHILE @ID IS NOT NULL BEGIN
PRINT @ID; SET @ID = (SELECT MIN(ID) FROM TABLE WHERE ID > @ID); END
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Chapter 22: OVER Clause
Parameter Details PARTITION BY The field(s) that follows PARTITION BY is the one that the 'grouping' will be based on
Section 22.1: Cumulative Sum
Using the Item Sales Table, we will try to find out how the sales of our items are increasing through dates. To do so we will calculate the Cumulative Sum of total sales per Item order by the sale date.
SELECT item_id, sale_Date
SUM(quantity * price) OVER(PARTITION BY item_id ORDER BY sale_Date ROWS BETWEEN UNBOUNDED PRECEDING) AS SalesTotal
FROM SalesTable
Section 22.2: Using Aggregation functions with OVER
Using the Cars Table, we will calculate the total, max, min and average amount of money each costumer spent and haw many times (COUNT) she brought a car for repairing.
Id CustomerId MechanicId Model Status Total Cost
SELECT CustomerId,
SUM(TotalCost) OVER(PARTITION BY CustomerId) AS Total, AVG(TotalCost) OVER(PARTITION BY CustomerId) AS Avg, COUNT(TotalCost) OVER(PARTITION BY CustomerId) AS Count, MIN(TotalCost) OVER(PARTITION BY CustomerId) AS Min, MAX(TotalCost) OVER(PARTITION BY CustomerId) AS Max FROM CarsTable WHERE Status = 'READY'
Beware that using OVER in this fashion will not aggregate the rows returned. The above query will return the following:
CustomerId Total Avg Count Min Max 1 430 215 2 200 230
1 430 215 2 200 230
The duplicated row(s) may not be that useful for reporting purposes.
If you wish to simply aggregate data, you will be better off using the GROUP BY clause along with the appropriate aggregate functions Eg:
SELECT CustomerId,
SUM(TotalCost) AS Total, AVG(TotalCost) AS Avg, COUNT(TotalCost) AS Count, MIN(TotalCost) AS Min, MAX(TotalCost) AS Max FROM CarsTable WHERE Status = 'READY' GROUP BY CustomerId
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Section 22.3: Dividing Data into equally-partitioned buckets using NTILE
Let's say that you have exam scores for several exams and you want to divide them into quartiles per exam.
-- Setup data: declare @values table(Id int identity(1,1) primary key, [Value] float, ExamId int) insert into @values ([Value], ExamId) values (65, 1), (40, 1), (99, 1), (100, 1), (90, 1), -- Exam 1 Scores (91, 2), (88, 2), (83, 2), (91, 2), (78, 2), (67, 2), (77, 2) -- Exam 2 Scores
-- Separate into four buckets per exam: select ExamId,
ntile(4) over (partition by ExamId order by [Value] desc) as Quartile, Value, Id from @values order by ExamId, Quartile
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ntile works great when you really need a set number of buckets and each filled to approximately the same level. Notice that it would be trivial to separate these scores into percentiles by simply using ntile(100).
Section 22.4: Using Aggregation funtions to find the most recent records
Using the Library Database, we try to find the last book added to the database for each author. For this simple example we assume an always incrementing Id for each record added.
SELECT MostRecentBook.Name, MostRecentBook.Title FROM ( SELECT Authors.Name,
Books.Title, RANK() OVER (PARTITION BY Authors.Id ORDER BY Books.Id DESC) AS NewestRank FROM Authors JOIN Books ON Books.AuthorId = Authors.Id ) MostRecentBook WHERE MostRecentBook.NewestRank = 1
Instead of RANK, two other functions can be used to order. In the previous example the result will be the same, but they give different results when the ordering gives multiple rows for each rank.
RANK(): duplicates get the same rank, the next rank takes the number of duplicates in the previous rank into account
DENSE_RANK(): duplicates get the same rank, the next rank is always one higher than the previous ROW_NUMBER(): will give each row a unique 'rank', 'ranking' the duplicates randomly
For example, if the table had a non-unique column CreationDate and the ordering was done based on that, the following query:
SELECT Authors.Name,
Books.Title, Books.CreationDate, RANK() OVER (PARTITION BY Authors.Id ORDER BY Books.CreationDate DESC) AS RANK, DENSE_RANK() OVER (PARTITION BY Authors.Id ORDER BY Books.CreationDate DESC) AS DENSE_RANK, ROW_NUMBER() OVER (PARTITION BY Authors.Id ORDER BY Books.CreationDate DESC) AS ROW_NUMBER, FROM Authors JOIN Books ON Books.AuthorId = Authors.Id
Could result in:
Author Title CreationDate RANK DENSE_RANK ROW_NUMBER Author 1 Book 1 22/07/2016 1 1 1
Author 1 Book 2 22/07/2016 1 1 2 Author 1 Book 3 21/07/2016 3 2 3
Author 1 Book 4 21/07/2016 3 2 4
Author 1 Book 5 21/07/2016 3 2 5
Author 1 Book 6 04/07/2016 6 3 6 Author 2 Book 7 04/07/2016 1 1 1
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Chapter 23: GROUP BY
Section 23.1: Simple Grouping
Orders Table
CustomerId ProductId Quantity Price 1 2 5 100
1 3 2 200
1 4 1 500
2 1 4 50 3 5 6 700
When grouping by a specific column, only unique values of this column are returned.
SELECT customerId FROM orders GROUP BY customerId;
Return value:
customerId 1 2
3
Aggregate functions like count() apply to each group and not to the complete table:
SELECT customerId,
COUNT(productId) as numberOfProducts, sum(price) as totalPrice FROM orders GROUP BY customerId;
Return value:
customerId numberOfProducts totalPrice 1 3 800
2 1 50
3 1 700
Section 23.2: GROUP BY multiple columns
One might want to GROUP BY more than one column
declare @temp table(age int, name varchar(15))
insert into @temp select 18, 'matt' union all select 21, 'matt' union all select 21, 'matt' union all select 18, 'luke' union all select 18, 'luke' union all select 21, 'luke' union all
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select 18, 'luke' union all select 21, 'luke'
SELECT Age, Name, count(1) count FROM @temp GROUP BY Age, Name
will group by both age and name and will produce:
Age Name count 18 luke 3 21 luke 2
18 matt 1
21 matt 2
Section 23.3: GROUP BY with ROLLUP and CUBE
The ROLLUP operator is useful in generating reports that contain subtotals and totals.
CUBE generates a result set that shows aggregates for all combinations of values in the selected columns.
ROLLUP generates a result set that shows aggregates for a hierarchy of values in the selected columns.
Item Color Quantity Table Blue 124
Table Red 223 Chair Blue 101
Chair Red 210
SELECT CASE WHEN (GROUPING(Item) = 1) THEN 'ALL'
ELSE ISNULL(Item, 'UNKNOWN') END AS Item, CASE WHEN (GROUPING(Color) = 1) THEN 'ALL'
ELSE ISNULL(Color, 'UNKNOWN') END AS Color, SUM(Quantity) AS QtySum FROM Inventory GROUP BY Item, Color WITH ROLLUP
Item Color QtySum -------------------- -------------------- -------------------------- Chair Blue 101.00 Chair Red 210.00 Chair ALL 311.00 Table Blue 124.00 Table Red 223.00 Table ALL 347.00 ALL ALL 658.00
(7 row(s) affected)
If the ROLLUP keyword in the query is changed to CUBE, the CUBE result set is the same, except these two additional rows are returned at the end:
ALL Blue 225.00
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ALL Red 433.00
https://technet.microsoft.com/en-us/library/ms189305(v=sql.90).aspx
Section 23.4: Group by with multiple tables, multiple columns
Group by is often used with join statement. Let's assume we have two tables. The first one is the table of students:
Id Full Name Age 1 Matt Jones 20 2 Frank Blue 21
3 Anthony Angel 18
Second table is the table of subject each student can take:
Subject_Id Subject 1 Maths
2 P.E.
3 Physics
And because one student can attend many subjects and one subject can be attended by many students (therefore N:N relationship) we need to have third "bounding" table. Let's call the table Students_subjects:
Subject_Id Student_Id 1 1
2 2 2 1
3 2
1 3
1 1
Now lets say we want to know the number of subjects each student is attending. Here the standalone GROUP BY statement is not sufficient as the information is not available through single table. Therefore we need to use GROUP BY with the JOIN statement:
Select Students.FullName, COUNT(Subject Id) as SubjectNumber FROM Students_Subjects LEFT JOIN Students ON Students_Subjects.Student_id = Students.Id GROUP BY Students.FullName
The result of the given query is as follows:
FullName SubjectNumber Matt Jones 3 Frank Blue 2
Anthony Angel 1
For an even more complex example of GROUP BY usage, let's say student might be able to assign the same subject to his name more than once (as shown in table Students_Subjects). In this scenario we might be able to count number of times each subject was assigned to a student by GROUPing by more than one column:
SELECT Students.FullName, Subjects.Subject, COUNT(Students_subjects.Subject_id) AS NumberOfOrders
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FROM ((Students_Subjects INNER JOIN Students ON Students_Subjcets.Student_id=Students.Id) INNER JOIN Subjects ON Students_Subjects.Subject_id=Subjects.Subject_id) GROUP BY Fullname,Subject
This query gives the following result:
FullName Subject SubjectNumber Matt Jones Maths 2 Matt Jones P.E 1
Frank Blue P.E 1
Frank Blue Physics 1
Anthony Angel Maths 1
Section 23.5: HAVING
Because the WHERE clause is evaluated before GROUP BY, you cannot use WHERE to pare down results of the grouping (typically an aggregate function, such as COUNT(*)). To meet this need, the HAVING clause can be used.
For example, using the following data:
DECLARE @orders TABLE(OrderID INT, Name NVARCHAR(100))
INSERT INTO @orders VALUES ( 1, 'Matt' ), ( 2, 'John' ), ( 3, 'Matt' ), ( 4, 'Luke' ), ( 5, 'John' ), ( 6, 'Luke' ), ( 7, 'John' ), ( 8, 'John' ), ( 9, 'Luke' ), ( 10, 'John' ), ( 11, 'Luke' )
If we want to get the number of orders each person has placed, we would use
SELECT Name, COUNT(*) AS 'Orders' FROM @orders GROUP BY Name
and get
Name Orders Matt 2 John 5
Luke 4
However, if we want to limit this to individuals who have placed more than two orders, we can add a HAVING clause.
SELECT Name, COUNT(*) AS 'Orders' FROM @orders GROUP BY Name
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HAVING COUNT(*) > 2
will yield
Name Orders John 5
Luke 4
Note that, much like GROUP BY, the columns put in HAVING must exactly match their counterparts in the SELECT statement. If in the above example we had instead said
SELECT Name, COUNT(DISTINCT OrderID)
our HAVING clause would have to say
HAVING COUNT(DISTINCT OrderID) > 2
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Chapter 24: ORDER BY
Section 24.1: Simple ORDER BY clause
Using the Employees Table, below is an example to return the Id, FName and LName columns in (ascending) LName order:
SELECT Id, FName, LName FROM Employees ORDER BY LName
Returns:
Id FName LName 2 John Johnson
1 James Smith 4 Johnathon Smith
3 Michael Williams
To sort in descending order add the DESC keyword after the field parameter, e.g. the same query in LName descending order is:
SELECT Id, FName, LName FROM Employees ORDER BY LName DESC
Section 24.2: ORDER BY multiple fields
Multiple fields can be specified for the ORDER BY clause, in either ASCending or DESCending order.
For example, using the http://stackoverflow.com/documentation/sql/280/example-databases/1207/item-sales-table#t=2016072113140664 34211 table, we can return a query that sorts by SaleDate in ascending order, and Quantity in descending order.
SELECT ItemId, SaleDate, Quantity FROM [Item Sales] ORDER BY SaleDate ASC, Quantity DESC
Note that the ASC keyword is optional, and results are sorted in ascending order of a given field by default.
Section 24.3: Custom Ordering
If you want to order by a column using something other than alphabetical/numeric ordering, you can use case to specify the order you want.
order by Group returns:
Group Count Not Retired 6
Retired 4
Total 10
order by case group when 'Total' then 1 when 'Retired' then 2 else 3 end returns:
Group Count
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Total 10
Retired 4 Not Retired 6
Section 24.4: ORDER BY with complex logic
If we want to order the data differently for per group, we can add a CASE syntax to the ORDER BY. In this example, we want to order employees from Department 1 by last name and employees from Department 2 by salary.
Id FName LName PhoneNumber ManagerId DepartmentId Salary HireDate 1 James Smith 1234567890 NULL 1 1000 01-01-2002
2 John Johnson 2468101214 1 1 400 23-03-2005
3 Michael Williams 1357911131 1 2 600 12-05-2009
4 Johnathon Smith 1212121212 2 1 500 24-07-2016
5 Sam Saxon 1372141312 2 2 400 25-03-2015
The following query will provide the required results:
SELECT Id, FName, LName, Salary FROM Employees ORDER BY Case When DepartmentId = 1 then LName else Salary end
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Chapter 25: The STUFF Function
Parameter Details character_expression the existing string in your data
start_position
the position in character_expression to delete length and then insert the replacement_string
length the number of characters to delete from character_expression
replacement_string the sequence of characters to insert in character_expression
Section Multiple 25.1: Rows
Using FOR XML to Concatenate Values from
One common use for the FOR XML function is to concatenate the values of multiple rows.
Here's an example using the Customers table:
SELECT
STUFF( (SELECT ';' + Email
FROM Customers where (Email is not null and Email <> '') ORDER BY Email ASC FOR XML PATH('')), 1, 1, '')
In the example above, FOR XML PATH('')) is being used to concatenate email addresses, using ; as the delimiter character. Also, the purpose of STUFF is to remove the leading ; from the concatenated string. STUFF is also implicitly casting the concatenated string from XML to varchar.
Note: the result from the above example will be XML-encoded, meaning it will replace < characters with < etc. If you don't want this, change FOR XML PATH('')) to FOR XML PATH, TYPE).value('.[1]','varchar(MAX)'), e.g.:
SELECT
STUFF( (SELECT ';' + Email
FROM Customers where (Email is not null and Email <> '') ORDER BY Email ASC FOR XML PATH, TYPE).value('.[1]','varchar(900)'), 1, 1, '')
This can be used to achieve a result similar to GROUP_CONCAT in MySQL or string_agg in PostgreSQL 9.0+, although we use subqueries instead of GROUP BY aggregates. (As an alternative, you can install a user-defined aggregate such as this one if you're looking for functionality closer to that of GROUP_CONCAT).
Section 25.2: Basic Character Replacement with STUFF()
The STUFF() function inserts a string into another string by first deleting a specified number of characters. The following example, deletes "Svr" and replaces it with "Server". This happens by specifying the start_position and length of the replacement.
SELECT STUFF('SQL Svr Documentation', 5, 3, 'Server')
Executing this example will result in returning SQL Server Documentation instead of SQL Svr Documentation.
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Section 25.3: Basic Example of STUFF() function
STUFF(Original_Expression, Start, Length, Replacement_expression)
STUFF() function inserts Replacement_expression, at the start position specified, along with removing the characters specified using Length parameter.
Select FirstName, LastName,Email, STUFF(Email, 2, 3, '*****') as StuffedEmail From Employee
Executing this example will result in returning the given table
FirstNameLastName Email StuffedEmail Jomes Hunter James@hotmail.com J*****s@hotmail.com
Shyam rathod Shyam@hotmail.com S*****m@hotmail.com Ram shinde Ram@hotmail.com R*****hotmail.com
Section 25.4: stu for comma separated in sql server
FOR XML PATH and STUFF to concatenate the multiple rows into a single row:
select distinct t1.id,
STUFF(
(SELECT ', ' + convert(varchar(10), t2.date, 120)
FROM yourtable t2 where t1.id = t2.id FOR XML PATH ('')) , 1, 1, '') AS date from yourtable t1;
Section 25.5: Obtain column names separated with comma (not a list)
/* The result can be use for fast way to use columns on Insertion/Updates. Works with tables and views.
Example: eTableColumns 'Customers' ColumnNames ------------------------------------------------------ Id, FName, LName, Email, PhoneNumber, PreferredContact
INSERT INTO Customers (Id, FName, LName, Email, PhoneNumber, PreferredContact)
VALUES (5, 'Ringo', 'Star', 'two@beatles.now', NULL, 'EMAIL') */ CREATE PROCEDURE eTableColumns (@Table VARCHAR(100)) AS SELECT ColumnNames =
STUFF( (SELECT ', ' + c.name FROM
sys.columns c INNER JOIN
sys.types t ON c.user_type_id = t.user_type_id WHERE
c.object_id = OBJECT_ID( @Table)
FOR XML PATH, TYPE).value('.[1]','varchar(2000)'), 1, 1, '')
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GO
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Chapter 26: JSON in SQL Server
Parameters Details expression Typically the name of a variable or a column that contains JSON text.
path
A JSON path expression that specifies the property to update. path has the following syntax: [append] [ lax | strict ] $.<json path>
jsonExpression Is a Unicode character expression containing the JSON text.
Section columns
26.1: Index on JSON properties by using computed
When storing JSON documents in SQL Server, We need to be able to efficiently filter and sort query results on properties of the JSON documents.
CREATE TABLE JsonTable (
id int identity primary key, jsonInfo nvarchar(max), CONSTRAINT [Content should be formatted as JSON] CHECK (ISJSON(jsonInfo)>0) )
INSERT INTO JsonTable VALUES(N'{"Name":"John","Age":23}'), (N'{"Name":"Jane","Age":31}'), (N'{"Name":"Bob","Age":37}'), (N'{"Name":"Adam","Age":65}') GO
Given the above table If we want to find the row with the name = 'Adam', we would execute the following query.
SELECT * FROM JsonTable Where JSON_VALUE(jsonInfo, '$.Name') = 'Adam'
However this will require SQL server to perform a full table which on a large table is not efficent.
To speed this up we would like to add an index, however we cannot directly reference properties in the JSON document. The solution is to add a computed column on the JSON path $.Name, then add an index on the computed column.
ALTER TABLE JsonTable ADD vName as JSON_VALUE(jsonInfo, '$.Name')
CREATE INDEX idx_name ON JsonTable(vName)
Now when we execute the same query, instead of a full table scan SQL server uses an index to seek into the non- clustered index and find the rows that satisfy the specified conditions.
Note: For SQL server to use the index, you must create the computed column with the same expression that you plan to use in your queries - in this example JSON_VALUE(jsonInfo, '$.Name'), however you can also use the name of computed column vName
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Section 26.2: Join parent and child JSON entities using CROSS APPLY OPENJSON
Join parent objects with their child entities, for example we want a relational table of each person and their hobbies
DECLARE @json nvarchar(1000) = N'[
{
"id":1, "user":{"name":"John"}, "hobbies":[
{"name": "Reading"}, {"name": "Surfing"} ] }, {
"id":2, "user":{"name":"Jane"}, "hobbies":[
{"name": "Programming"}, {"name": "Running"} ] } ]'
Query
SELECT
JSON_VALUE(person.value, '$.id') as Id, JSON_VALUE(person.value, '$.user.name') as PersonName, JSON_VALUE(hobbies.value, '$.name') as Hobby FROM OPENJSON (@json) as person
CROSS APPLY OPENJSON(person.value, '$.hobbies') as hobbies
Alternatively this query can be written using the WITH clause.
SELECT
Id, person.PersonName, Hobby FROM OPENJSON (@json) WITH(
Id int '$.id', PersonName nvarchar(100) '$.user.name', Hobbies nvarchar(max) '$.hobbies' AS JSON ) as person CROSS APPLY OPENJSON(Hobbies) WITH(
Hobby nvarchar(100) '$.name' )
Result
Id PersonName Hobby 1 John Reading 1 John Surfing
2 Jane Programming
2 Jane Running
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Section 26.3: Format Query Results as JSON with FOR JSON
Input table data (People table)
Id Name Age 1 John 23
2 Jane 31
Query
SELECT Id, Name, Age FROM People FOR JSON PATH
Result
[
{"Id":1,"Name":"John","Age":23}, {"Id":2,"Name":"Jane","Age":31} ]
Section 26.4: Parse JSON text
JSON_VALUE and JSON_QUERY functions parse JSON text and return scalar values or objects/arrays on the path in JSON text.
DECLARE @json NVARCHAR(100) = '{"id": 1, "user":{"name":"John"}, "skills":["C#","SQL"]}'
SELECT
JSON_VALUE(@json, '$.id') AS Id, JSON_VALUE(@json, '$.user.name') AS Name, JSON_QUERY(@json, '$.user') AS UserObject, JSON_QUERY(@json, '$.skills') AS Skills, JSON_VALUE(@json, '$.skills[0]') AS Skill0
Result
Id Name UserObject Skills Skill0 1 John {"name":"John"} ["C#","SQL"] C#
Section 26.5: Format one table row as a single JSON object using FOR JSON
WITHOUT_ARRAY_WRAPPER option in FOR JSON clause will remove array brackets from the JSON output. This is useful if you are returning single row in the query.
Note: this option will produce invalid JSON output if more than one row is returned.
Input table data (People table)
Id Name Age 1 John 23
2 Jane 31
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Query
SELECT Id, Name, Age FROM People WHERE Id = 1 FOR JSON PATH, WITHOUT_ARRAY_WRAPPER
Result
{"Id":1,"Name":"John","Age":23}
Section 26.6: Parse JSON text using OPENJSON function
OPENJSON function parses JSON text and returns multiple outputs. Values that should be returned are specified using the paths defined in the WITH clause. If a path is not specified for some column, the column name is used as a path. This function casts returned values to the SQL types defined in the WITH clause. AS JSON option must be specified in the column definition if some object/array should be returned.
DECLARE @json NVARCHAR(100) = '{"id": 1, "user":{"name":"John"}, "skills":["C#","SQL"]}'
SELECT * FROM OPENJSON (@json)
WITH(Id int '$.id',
Name nvarchar(100) '$.user.name', UserObject nvarchar(max) '$.user' AS JSON, Skills nvarchar(max) '$.skills' AS JSON, Skill0 nvarchar(20) '$.skills[0]')
Result
Id Name UserObject Skills Skill0 1 John {"name":"John"} ["C#","SQL"] C#
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Chapter 27: OPENJSON
Section 27.1: Transform JSON array into set of rows
OPENJSON function parses collection of JSON objects and returns values from JSON text as set of rows.
declare @json nvarchar(4000) = N'[
{"Number":"SO43659","Date":"2011-05-31T00:00:00","Customer": "MSFT","Price":59.99,"Quantity":1}, {"Number":"SO43661","Date":"2011-06-01T00:00:00","Customer":"Nokia","Price":24.99,"Quantity":3} ]'
SELECT * FROM OPENJSON (@json)
WITH (
Number varchar(200), Date datetime, Customer varchar(200), Quantity int )
In the WITH clause is specified return schema of OPENJSON function. Keys in the JSON objects are fetched by column names. If some key in JSON is not specified in the WITH clause (e.g. Price in this example) it will be ignored. Values are automatically converted into specified types.
Number Date Customer Quantity SO43659 2011-05-31T00:00:00 MSFT 1
SO43661 2011-06-01T00:00:00 Nokia 3
Section 27.2: Get key:value pairs from JSON text
OPENJSON function parse JSON text and returns all key:value pairs at the first level of JSON:
declare @json NVARCHAR(4000) = N'{"Name":"Joe","age":27,"skills":["C#","SQL"]}'; SELECT * FROM OPENJSON(@json);
key value type Name Joe 1
age 27 2 skills ["C#","SQL"] 4
Column type describe the type of value, i.e. null(0), string(1), number(2), boolean(3), array(4), and object(5).
Section 27.3: Transform nested JSON fields into set of rows
OPENJSON function parses collection of JSON objects and returns values from JSON text as set of rows. If the values in input object are nested, additional mapping parameter can be specified in each column in WITH clause:
declare @json nvarchar(4000) = N'[
{"data":{"num":"SO43659","date":"2011-05-31T00:00:00"},"info":{"customer":"MSFT","Price":59.99,"qty ":1}},
{"data":{"number":"SO43661","date":"2011-06-01T00:00:00"},"info":{"customer":"Nokia","Price":24.99, "qty":3}} ]'
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SELECT * FROM OPENJSON (@json)
WITH (
Number varchar(200) '$.data.num', Date datetime '$.data.date', Customer varchar(200) '$.info.customer', Quantity int '$.info.qty', )
In the WITH clause is specified return schema of OPENJSON function. After the type is specified path to the JSON nodes where returned value should be found. Keys in the JSON objects are fetched by these paths. Values are automatically converted into specified types.
Number Date Customer Quantity SO43659 2011-05-31T00:00:00 MSFT 1
SO43661 2011-06-01T00:00:00 Nokia 3
Section 27.4: Extracting inner JSON sub-objects
OPENJSON can extract fragments of JSON objects inside the JSON text. In the column definition that references JSON sub-object set the type nvarchar(max) and AS JSON option:
declare @json nvarchar(4000) = N'[
{"Number":"SO43659","Date":"2011-05-31T00:00:00","info":{"customer":"MSFT","Price":59.99,"qty":1}},
{"Number":"SO43661","Date":"2011-06-01T00:00:00","info":{"customer":"Nokia","Price":24.99,"qty":3}} ]'
SELECT * FROM OPENJSON (@json)
WITH (
Number varchar(200), Date datetime, Info nvarchar(max) '$.info' AS JSON )
Info column will be mapped to "Info" object. Results will be:
Number Date Info SO43659 2011-05-31T00:00:00 {"customer":"MSFT","Price":59.99,"qty":1}
SO43661 2011-06-01T00:00:00 {"customer":"Nokia","Price":24.99,"qty":3}
Section 27.5: Working with nested JSON sub-arrays
JSON may have complex structure with inner arrays. In this example, we have array of orders with nested sub array of OrderItems.
declare @json nvarchar(4000) = N'[
{"Number":"SO43659","Date":"2011-05-31T00:00:00",
"Items":[{"Price":11.99,"Quantity":1},{"Price":12.99,"Quantity":5}]}, {"Number":"SO43661","Date":"2011-06-01T00:00:00",
"Items":[{"Price":21.99,"Quantity":3},{"Price":22.99,"Quantity":2},{"Price":23.99,"Quantity":2}]} ]'
We can parse root level properties using OPENJSON that will return Items array AS JSON fragment. Then we can
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apply OPENJSON again on Items array and open inner JSON table. First level table and inner table will be "joined" like in the JOIN between standard tables:
SELECT * FROM
OPENJSON (@json) WITH ( Number varchar(200), Date datetime,
Items nvarchar(max) AS JSON ) CROSS APPLY
OPENJSON (Items) WITH ( Price float, Quantity int)
Results:
Number Date Items Price Quantity
SO43659
2011-05-31 00:00:00.000
[{"Price":11.99,"Quantity":1},{"Price":12.99,"Quantity":5}] 11.99 1
SO43659
2011-05-31 00:00:00.000
[{"Price":11.99,"Quantity":1},{"Price":12.99,"Quantity":5}] 12.99 5
SO43661
2011-06-01 00:00:00.000
[{"Price":21.99,"Quantity":3},{"Price":22.99,"Quantity":2},{"Price":23.99,"Quantity":2}] 21.99 3
SO43661
2011-06-01 00:00:00.000
[{"Price":21.99,"Quantity":3},{"Price":22.99,"Quantity":2},{"Price":23.99,"Quantity":2}] 22.99 2
SO43661
2011-06-01 00:00:00.000
[{"Price":21.99,"Quantity":3},{"Price":22.99,"Quantity":2},{"Price":23.99,"Quantity":2}] 23.99 2
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Chapter 28: FOR JSON
Section 28.1: FOR JSON PATH
Formats results of SELECT query as JSON text. FOR JSON PATH clause is added after query:
SELECT top 3 object_id, name, type, principal_id FROM sys.objects FOR JSON PATH
Column names will be used as keys in JSON, and cell values will be generated as JSON values. Result of the query would be an array of JSON objects:
[
{"object_id":3,"name":"sysrscols","type":"S "}, {"object_id":5,"name":"sysrowsets","type":"S "}, {"object_id":6,"name":"sysclones","type":"S "} ]
NULL values in principal_id column will be ignored (they will not be generated).
Section 28.2: FOR JSON PATH with column aliases
FOR JSON PATH enables you to control format of the output JSON using column aliases:
SELECT top 3 object_id as id, name as [data.name], type as [data.type] FROM sys.objects FOR JSON PATH
Column alias will be used as a key name. Dot-separated column aliases (data.name and data.type) will be generated as nested objects. If two column have the same prefix in dot notation, they will be grouped together in single object (data in this example):
[
{"id":3,"data":{"name":"sysrscols","type":"S "}}, {"id":5,"data":{"name":"sysrowsets","type":"S "}}, {"id":6,"data":{"name":"sysclones","type":"S "}} ]
Section 28.3: FOR JSON clause without array wrapper (single object in output)
WITHOUT_ARRAY_WRAPPER option enables you to generate a single object instead of the array. Use this option if you know that you will return single row/object:
SELECT top 3 object_id, name, type, principal_id FROM sys.objects WHERE object_id = 3 FOR JSON PATH, WITHOUT_ARRAY_WRAPPER
Single object will be returned in this case:
{"object_id":3,"name":"sysrscols","type":"S "}
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Section 28.4: INCLUDE_NULL_VALUES
FOR JSON clause ignores NULL values in cells. If you want to generate "key": null pairs for cells that contain NULL values, add INCLUDE_NULL_VALUES option in the query:
SELECT top 3 object_id, name, type, principal_id FROM sys.objects FOR JSON PATH, INCLUDE_NULL_VALUES
NULL values in principal_id column will be generated:
[
{"object_id":3,"name":"sysrscols","type":"S ","principal_id":null}, {"object_id":5,"name":"sysrowsets","type":"S ","principal_id":null}, {"object_id":6,"name":"sysclones","type":"S ","principal_id":null} ]
Section 28.5: Wrapping results with ROOT object
Wraps returned JSON array in additional root object with specified key:
SELECT top 3 object_id, name, type FROM sys.objects FOR JSON PATH, ROOT('data')
Result of the query would be array of JSON objects inside the wrapper object:
{
"data":[
{"object_id":3,"name":"sysrscols","type":"S "}, {"object_id":5,"name":"sysrowsets","type":"S "}, {"object_id":6,"name":"sysclones","type":"S "} ] }
Section 28.6: FOR JSON AUTO
Automatically nests values from the second table as a nested sub-array of JSON objects:
SELECT top 5 o.object_id, o.name, c.column_id, c.name FROM sys.objects o
JOIN sys.columns c ON o.object_id = c.object_id FOR JSON AUTO
Result of the query would be array of JSON objects:
[
{
"object_id":3, "name":"sysrscols", "c":[
{"column_id":12,"name":"bitpos"}, {"column_id":6,"name":"cid"} ] }, {
"object_id":5, "name":"sysrowsets",
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"c":[
{"column_id":13,"name":"colguid"}, {"column_id":3,"name":"hbcolid"}, {"column_id":8,"name":"maxinrowlen"} ] } ]
Section 28.7: Creating custom nested JSON structure
If you need some complex JSON structure that cannot be created using FOR JSON PATH or FOR JSON AUTO, you can customize your JSON output by putting FOR JSON sub-queries as column expressions:
SELECT top 5 o.object_id, o.name, (SELECT column_id, c.name
FROM sys.columns c WHERE o.object_id = c.object_id FOR JSON PATH) as columns, (SELECT parameter_id, name
FROM sys.parameters p WHERE o.object_id = p.object_id FOR JSON PATH) as parameters FROM sys.objects o FOR JSON PATH
Each sub-query will produce JSON result that will be included in the main JSON content.
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Chapter 29: Queries with JSON data
Section 29.1: Using values from JSON in query
JSON_VALUE function enables you to take a data from JSON text on the path specified as the second argument, and use this value in any part of the select query:
select ProductID, Name, Color, Size, Price, JSON_VALUE(Data, '$.Type') as Type from Product where JSON_VALUE(Data, '$.Type') = 'part'
Section 29.2: Using JSON values in reports
Once JSON values are extracted from JSON text, you can use them ina any part of the query. You can create some kind of report on JSON data with grouping aggregations, etc:
select JSON_VALUE(Data, '$.Type') as type,
AVG( cast(JSON_VALUE(Data, '$.ManufacturingCost') as float) ) as cost from Product group by JSON_VALUE(Data, '$.Type') having JSON_VALUE(Data, '$.Type') is not null
Section 29.3: Filter-out bad JSON text from query results
If some JSON text might not be properly formatted, you can remove those entries from query using ISJSON function.
select ProductID, Name, Color, Size, Price, JSON_VALUE(Data, '$.Type') as Type from Product where JSON_VALUE(Data, '$.Type') = 'part' and ISJSON(Data) > 0
Section 29.4: Update value in JSON column
JSON_MODIFY function can be used to update value on some path. You can use this function to modify original value of JSON cell in UPDATE statement:
update Product set Data = JSON_MODIFY(Data, '$.Price', 24.99) where ProductID = 17;
JSON_MODIFY function will update or create Price key (if it does not exists). If new value is NULL, the key will be removed. JSON_MODIFY function will treat new value as string (escape special characters, wrap it with double quotes to create proper JSON string). If your new value is JSON fragment, you should wrap it with JSON_QUERY function:
update Product set Data = JSON_MODIFY(Data, '$.tags', JSON_QUERY('["promo","new"]')) where ProductID = 17;
JSON_QUERY function without second parameter behaves like a "cast to JSON". Since the result of JSON_QUERY is valid JSON fragment (object or array), JSON_MODIFY will no escape this value when modifies input JSON.
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Section 29.5: Append new value into JSON array
JSON_MODIFY function can be used to append new value to some array inside JSON:
update Product set Data = JSON_MODIFY(Data, 'append $.tags', "sales") where ProductID = 17;
New value will be appended at the end of the array, or a new array with value ["sales"] will be created. JSON_MODIFY function will treat new value as string (escape special characters, wrap it with double quotes to create proper JSON string). If your new value is JSON fragment, you should wrap it with JSON_QUERY function:
update Product set Data = JSON_MODIFY(Data, 'append $.tags', JSON_QUERY('{"type":"new"}')) where ProductID = 17;
JSON_QUERY function without second parameter behaves like a "cast to JSON". Since the result of JSON_QUERY is valid JSON fragment (object or array), JSON_MODIFY will no escape this value when modifies input JSON.
Section 29.6: JOIN table with inner JSON collection
If you have a "child table" formatted as JSON collection and stored in-row as JSON column, you can unpack this collection, transform it to table and join it with parent row. Instead of the standard JOIN operator, you should use CROSS APPLY. In this example, product parts are formatted as collection of JSON objects in and stored in Data column:
select ProductID, Name, Size, Price, Quantity, PartName, Code from Product
CROSS APPLY OPENJSON(Data, '$.Parts') WITH (PartName varchar(20), Code varchar(5))
Result of the query is equivalent to the join between Product and Part tables.
Section 29.7: Finding rows that contain value in the JSON array
In this example, Tags array may contain various keywords like ["promo", "sales"], so we can open this array and filter values:
select ProductID, Name, Color, Size, Price, Quantity from Product
CROSS APPLY OPENJSON(Data, '$.Tags') where value = 'sales'
OPENJSON will open inner collection of tags and return it as table. Then we can filter results by some value in the table.
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Chapter 30: Storing JSON in SQL tables
Section 30.1: JSON stored as text column
JSON is textual format, so it is stored in standard NVARCHAR columns. NoSQL collection is equivalent to two column key value table:
CREATE TABLE ProductCollection ( Id int identity primary key, Data nvarchar(max) )
Use nvarchar(max) as you are not sure what would be the size of your JSON documents. nvarchar(4000) and varchar(8000) have better performance but with size limit to 8KB.
Section 30.2: Ensure that JSON is properly formatted using ISJSON
Since JSON is stored textual column, you might want to ensure that it is properly formatted. You can add CHECK constraint on JSON column that checks is text properly formatted JSON:
CREATE TABLE ProductCollection ( Id int identity primary key, Data nvarchar(max)
CONSTRAINT [Data should be formatted as JSON] CHECK (ISJSON(Data) > 0) )
If you already have a table, you can add check constraint using the ALTER TABLE statement:
ALTER TABLE ProductCollection
ADD CONSTRAINT [Data should be formatted as JSON]
CHECK (ISJSON(Data) > 0)
Section 30.3: Expose values from JSON text as computed columns
You can expose values from JSON column as computed columns:
CREATE TABLE ProductCollection ( Id int identity primary key, Data nvarchar(max), Price AS JSON_VALUE(Data, '$.Price'), Color JSON_VALUE(Data, '$.Color') PERSISTED )
If you add PERSISTED computed column, value from JSON text will be materialized in this column. This way your queries can faster read value from JSON text because no parsing is needed. Each time JSON in this row changes, value will be re-calculated.
Section 30.4: Adding index on JSON path
Queries that filter or sort data by some value in JSON column usually use full table scan.
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SELECT * FROM ProductCollection WHERE JSON_VALUE(Data, '$.Color') = 'Black'
To optimize these kind of queries, you can add non-persisted computed column that exposes JSON expression used in filter or sort (in this example JSON_VALUE(Data, '$.Color')), and create index on this column:
ALTER TABLE ProductCollection ADD vColor as JSON_VALUE(Data, '$.Color')
CREATE INDEX idx_JsonColor ON ProductCollection(vColor)
Queries will use the index instead of plain table scan.
Section 30.5: JSON stored in in-memory tables
If you can use memory-optimized tables, you can store JSON as text:
CREATE TABLE ProductCollection (
Id int identity primary key nonclustered, Data nvarchar(max) ) WITH (MEMORY_OPTIMIZED=ON)
Advantages of JSON in in-memory:
JSON data is always in memory so there is no disk access There are no locks and latches while working with JSON
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Chapter 31: Modify JSON text
Section 31.1: Modify value in JSON text on the specified path
JSON_MODIFY function uses JSON text as input parameter, and modifies a value on the specified path using third argument:
declare @json nvarchar(4000) = N'{"Id":1,"Name":"Toy Car","Price":34.99}' set @json = JSON_MODIFY(@json, '$.Price', 39.99) print @json -- Output: {"Id":1,"Name":"Toy Car","Price":39.99}
As a result, we will have new JSON text with "Price":39.99 and other value will not be changed. If object on the specified path does not exists, JSON_MODIFY will insert key:value pair.
In order to delete key:value pair, put NULL as new value:
declare @json nvarchar(4000) = N'{"Id":1,"Name":"Toy Car","Price":34.99}' set @json = JSON_MODIFY(@json, '$.Price', NULL) print @json -- Output: {"Id":1,"Name":"Toy Car"}
JSON_MODIFY will by default delete key if it does not have value so you can use it to delete a key.
Section 31.2: Append a scalar value into a JSON array
JSON_MODIFY has 'append' mode that appends value into array.
declare @json nvarchar(4000) = N'{"Id":1,"Name":"Toy Car","Tags":["toy","game"]}' set @json = JSON_MODIFY(@json, 'append $.Tags', 'sales') print @json -- Output: {"Id":1,"Name":"Toy Car","Tags":["toy","game","sales"]}
If array on the specified path does not exists, JSON_MODIFY(append) will create new array with a single element:
declare @json nvarchar(4000) = N'{"Id":1,"Name":"Toy Car","Price":34.99}' set @json = JSON_MODIFY(@json, 'append $.Tags', 'sales') print @json -- Output {"Id":1,"Name":"Toy Car","Tags":["sales"]}
Section 31.3: Insert new JSON Object in JSON text
JSON_MODIFY function enables you to insert JSON objects into JSON text:
declare @json nvarchar(4000) = N'{"Id":1,"Name":"Toy Car"}' set @json = JSON_MODIFY(@json, '$.Price',
JSON_QUERY('{"Min":34.99,"Recommended":45.49}')) print @json -- Output: {"Id":1,"Name":"Toy Car","Price":{"Min":34.99,"Recommended":45.49}}
Since third parameter is text you need to wrap it with JSON_QUERY function to "cast" text to JSON. Without this "cast", JSON_MODIFY will treat third parameter as plain text and escape characters before inserting it as string value. Without JSON_QUERY results will be:
{"Id":1,"Name":"Toy Car","Price":'{\"Min\":34.99,\"Recommended\":45.49}'}
JSON_MODIFY will insert this object if it does not exist, or delete it if value of third parameter is NULL.
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Section 31.4: Insert new JSON array generated with FOR JSON query
You can generate JSON object using standard SELECT query with FOR JSON clause and insert it into JSON text as third parameter:
declare @json nvarchar(4000) = N'{"Id":17,"Name":"WWI"}' set @json = JSON_MODIFY(@json, '$.tables',
(select name from sys.tables FOR JSON PATH) ) print @json
(1 row(s) affected)
{"Id":1,"Name":"master","tables":[{"name":"Colors"},{"name":"Colors_Archive"},{"name":"OrderLines"} ,{"name":"PackageTypes"},{"name":"PackageTypes_Archive"},{"name":"StockGroups"},{"name":"StockItemS tockGroups"},{"name":"StockGroups_Archive"},{"name":"StateProvinces"},{"name":"CustomerTransactions "},{"name":"StateProvinces_Archive"},{"name":"Cities"},{"name":"Cities_Archive"},{"name":"SystemPar ameters"},{"name":"InvoiceLines"},{"name":"Suppliers"},{"name":"StockItemTransactions"},{"name":"Su ppliers_Archive"},{"name":"Customers"},{"name":"Customers_Archive"},{"name":"PurchaseOrders"},{"nam e":"Orders"},{"name":"People"},{"name":"StockItems"},{"name":"People_Archive"},{"name":"ColdRoomTem peratures"},{"name":"ColdRoomTemperatures_Archive"},{"name":"VehicleTemperatures"},{"name":"StockIt ems_Archive"},{"name":"Countries"},{"name":"StockItemHoldings"},{"name":"sysdiagrams"},{"name":"Pur chaseOrderLines"},{"name":"Countries_Archive"},{"name":"DeliveryMethods"},{"name":"DeliveryMethods_ Archive"},{"name":"PaymentMethods"},{"name":"SupplierTransactions"},{"name":"PaymentMethods_Archive "},{"name":"TransactionTypes"},{"name":"SpecialDeals"},{"name":"TransactionTypes_Archive"},{"name": "SupplierCategories"},{"name":"SupplierCategories_Archive"},{"name":"BuyingGroups"},{"name":"Invoic es"},{"name":"BuyingGroups_Archive"},{"name":"CustomerCategories"},{"name":"CustomerCategories_Arch ive"}]}
JSON_MODIFY will know that select query with FOR JSON clause generates valid JSON array and it will just insert it into JSON text.
You can use all FOR JSON options in SELECT query, except WITHOUT_ARRAY_WRAPPER, which will generate single object instead of JSON array. See other example in this topic to see how insert single JSON object.
Section 31.5: Insert single JSON object generated with FOR JSON clause
You can generate JSON object using standard SELECT query with FOR JSON clause and WITHOUT_ARRAY_WRAPPER option, and insert it into JSON text as a third parameter:
declare @json nvarchar(4000) = N'{"Id":17,"Name":"WWI"}' set @json = JSON_MODIFY(@json, '$.table',
JSON_QUERY(
(select name, create_date, schema_id
from sys.tables where name = 'Colors' FOR JSON PATH, WITHOUT_ARRAY_WRAPPER))) print @json
(1 row(s) affected)
{"Id":17,"Name":"WWI","table":{"name":"Colors","create_date":"2016-06-02T10:04:03.280","schema_id": 13}}
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FOR JSON with WITHOUT_ARRAY_WRAPPER option may generate invalid JSON text if SELECT query returns more than one result (you should use TOP 1 or filter by primary key in this case). Therefore, JSON_MODIFY will assume that returned result is just a plain text and escape it like any other text if you don't wrap it with JSON_QUERY function.
You should wrap FOR JSON, WITHOUT_ARRAY_WRAPPER query with JSON_QUERY function in order to cast result to JSON.
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Chapter 32: FOR XML PATH
Section 32.1: Using FOR XML PATH to concatenate values
The FOR XML PATH can be used for concatenating values into string. The example below concatenates values into a CSV string:
DECLARE @DataSource TABLE (
[rowID] TINYINT ,[FirstName] NVARCHAR(32) );
INSERT INTO @DataSource ([rowID], [FirstName]) VALUES (1, 'Alex')
,(2, 'Peter') ,(3, 'Alexsandyr') ,(4, 'George');
SELECT STUFF (
(
SELECT ',' + [FirstName] FROM @DataSource ORDER BY [rowID] DESC FOR XML PATH(''), TYPE ).value('.', 'NVARCHAR(MAX)') ,1 ,1 ,'' );
Few important notes:
the ORDER BY clause can be used to order the values in a preferred way if a longer value is used as the concatenation separator, the STUFF function parameter must be changed too;
SELECT STUFF (
(
SELECT '---' + [FirstName] FROM @DataSource ORDER BY [rowID] DESC FOR XML PATH(''), TYPE ).value('.', 'NVARCHAR(MAX)') ,1 ,3 -- the "3" could also be represented as: LEN('---') for clarity ,'' );
as the TYPE option and .value function are used, the concatenation works with NVARCHAR(MAX) string
Section 32.2: Specifying namespaces
Version ≥ SQL Server 2008
WITH XMLNAMESPACES (
DEFAULT 'http://www.w3.org/2000/svg', 'http://www.w3.org/1999/xlink' AS xlink
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) SELECT
'example.jpg' AS 'image/@xlink:href', '50px' AS 'image/@width', '50px' AS 'image/@height' FOR XML PATH('svg')
<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
<image xlink:href="firefox.jpg" width="50px" height="50px"/> </svg>
Section 32.3: Specifying structure using XPath expressions
SELECT
'XPath example' AS 'head/title', 'This example demonstrates ' AS 'body/p', 'https://www.w3.org/TR/xpath/' AS 'body/p/a/@href', 'XPath expressions' AS 'body/p/a' FOR XML PATH('html')
<html>
<head>
<title>XPath example</title> </head> <body>
<p>This example demonstrates <a href="https://www.w3.org/TR/xpath/">XPath expressions</a></p>
</body> </html>
In FOR XML PATH, columns without a name become text nodes. NULL or '' therefore become empty text nodes. Note: you can convert a named column to an unnamed one by using AS *
DECLARE @tempTable TABLE (Ref INT, Des NVARCHAR(100), Qty INT) INSERT INTO @tempTable VALUES (100001, 'Normal', 1), (100002, 'Foobar', 1), (100003, 'Hello World', 2)
SELECT ROW_NUMBER() OVER (ORDER BY Ref) AS '@NUM',
'REF' AS 'FLD/@NAME', REF AS 'FLD', '', 'DES' AS 'FLD/@NAME', DES AS 'FLD', '', 'QTY' AS 'FLD/@NAME', QTY AS 'FLD' FROM @tempTable FOR XML PATH('LIN'), ROOT('row')
<row>
<LIN NUM="1">
<FLD NAME="REF">100001</FLD> <FLD NAME="DES">Normal</FLD> <FLD NAME="QTY">1</FLD> </LIN> <LIN NUM="2">
<FLD NAME="REF">100002</FLD> <FLD NAME="DES">Foobar</FLD> <FLD NAME="QTY">1</FLD> </LIN> <LIN NUM="3">
<FLD NAME="REF">100003</FLD> <FLD NAME="DES">Hello World</FLD> <FLD NAME="QTY">2</FLD> </LIN> </row>
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Using (empty) text nodes helps to separate the previously output node from the next one, so that SQL Server knows to start a new element for the next column. Otherwise, it gets confused when the attribute already exists on what it thinks is the "current" element.
For example, without the the empty strings between the element and the attribute in the SELECT statement, SQL Server gives an error:
Attribute-centric column 'FLD/@NAME' must not come after a non-attribute-centric sibling in XML hierarchy in FOR XML PATH.
Also note that this example also wrapped the XML in a root element named row, specified by ROOT('row')
Section 32.4: Hello World XML
SELECT 'Hello World' FOR XML PATH('example')
<example>Hello World</example>
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Chapter 33: Join
In Structured Query Language (SQL), a JOIN is a method of linking two data tables in a single query, allowing the database to return a set that contains data from both tables at once, or using data from one table to be used as a Filter on the second table. There are several types of JOINs defined within the ANSI SQL standard.
Section 33.1: Inner Join
Inner join returns only those records/rows that match/exists in both the tables based on one or more conditions (specified using ON keyword). It is the most common type of join. The general syntax for inner join is:
SELECT * FROM table_1 INNER JOIN table_2
ON table_1.column_name = table_2.column_name
It can also be simplified as just JOIN:
SELECT * FROM table_1 JOIN table_2
ON table_1.column_name = table_2.column_name
Example
/* Sample data. */ DECLARE @Animal table (
AnimalId Int IDENTITY, Animal Varchar(20) );
DECLARE @AnimalSound table (
AnimalSoundId Int IDENTITY, AnimalId Int, Sound Varchar(20) );
INSERT INTO @Animal (Animal) VALUES ('Dog'); INSERT INTO @Animal (Animal) VALUES ('Cat'); INSERT INTO @Animal (Animal) VALUES ('Elephant');
INSERT INTO @AnimalSound (AnimalId, Sound) VALUES (1, 'Barks'); INSERT INTO @AnimalSound (AnimalId, Sound) VALUES (2, 'Meows'); INSERT INTO @AnimalSound (AnimalId, Sound) VALUES (3, 'Trumpets'); /* Sample data prepared. */
SELECT
* FROM
@Animal JOIN @AnimalSound
ON @Animal.AnimalId = @AnimalSound.AnimalId;
AnimalId Animal AnimalSoundId AnimalId Sound ----------- -------------------- ------------- ----------- -------------------- 1 Dog 1 1 Barks 2 Cat 2 2 Meows 3 Elephant 3 3 Trumpets
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Using inner join with left outer join (Substitute for Not exists)
This query will return data from table 1 where fields matching with table2 with a key and data not in Table 1 when comparing with Table2 with a condition and key
select *
from Table1 t1
inner join Table2 t2 on t1.ID_Column = t2.ID_Column left join Table3 t3 on t1.ID_Column = t3.ID_Column where t2.column_name = column_value
and t3.ID_Column is null order by t1.column_name;
Section 33.2: Outer Join
Left Outer Join
LEFT JOIN returns all rows from the left table, matched to rows from the right table where the ON clause conditions are met. Rows in which the ON clause is not met have NULL in all of the right table's columns. The syntax of a LEFT JOIN is:
SELECT * FROM table_1 AS t1 LEFT JOIN table_2 AS t2 ON t1.ID_Column = t2.ID_Column
Right Outer Join
RIGHT JOIN returns all rows from the right table, matched to rows from the left table where the ON clause conditions are met. Rows in which the ON clause is not met have NULL in all of the left table's columns. The syntax of a RIGHT JOIN is:
SELECT * FROM table_1 AS t1 RIGHT JOIN table_2 AS t2 ON t1.ID_Column = t2.ID_Column
Full Outer Join
FULL JOIN combines LEFT JOIN and RIGHT JOIN. All rows are returned from both tables, regardless of whether the conditions in the ON clause are met. Rows that do not satisfy the ON clause are returned with NULL in all of the opposite table's columns (that is, for a row in the left table, all columns in the right table will contain NULL, and vice versa). The syntax of a FULL JOIN is:
SELECT * FROM table_1 AS t1 FULL JOIN table_2 AS t2 ON t1.ID_Column = t2.ID_Column
Examples
/* Sample test data. */ DECLARE @Animal table (
AnimalId Int IDENTITY, Animal Varchar(20) );
DECLARE @AnimalSound table (
AnimalSoundId Int IDENTITY, AnimalId Int, Sound Varchar(20)
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);
INSERT INTO @Animal (Animal) VALUES ('Dog'); INSERT INTO @Animal (Animal) VALUES ('Cat'); INSERT INTO @Animal (Animal) VALUES ('Elephant'); INSERT INTO @Animal (Animal) VALUES ('Frog');
INSERT INTO @AnimalSound (AnimalId, Sound) VALUES (1, 'Barks'); INSERT INTO @AnimalSound (AnimalId, Sound) VALUES (2, 'Meows'); INSERT INTO @AnimalSound (AnimalId, Sound) VALUES (3, 'Trumpet'); INSERT INTO @AnimalSound (AnimalId, Sound) VALUES (5, 'Roars'); /* Sample data prepared. */
LEFT OUTER JOIN
SELECT * FROM @Animal As t1 LEFT JOIN @AnimalSound As t2 ON t1.AnimalId = t2.AnimalId;
Results for LEFT JOIN
AnimalId Animal AnimalSoundId AnimalId Sound ----------- -------------------- ------------- ----------- -------------------- 1 Dog 1 1 Barks 2 Cat 2 2 Meows 3 Elephant 3 3 Trumpet 4 Frog NULL NULL NULL
RIGHT OUTER JOIN
SELECT * FROM @Animal As t1 RIGHT JOIN @AnimalSound As t2 ON t1.AnimalId = t2.AnimalId;
Results for RIGHT JOIN
AnimalId Animal AnimalSoundId AnimalId Sound ----------- -------------------- ------------- ----------- -------------------- 1 Dog 1 1 Barks 2 Cat 2 2 Meows 3 Elephant 3 3 Trumpet NULL NULL 4 5 Roars
FULL OUTER JOIN
SELECT * FROM @Animal As t1 FULL JOIN @AnimalSound As t2 ON t1.AnimalId = t2.AnimalId;
Results for FULL JOIN
AnimalId Animal AnimalSoundId AnimalId Sound ----------- -------------------- ------------- ----------- -------------------- 1 Dog 1 1 Barks 2 Cat 2 2 Meows 3 Elephant 3 3 Trumpet
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4 Frog NULL NULL NULL NULL NULL 4 5 Roars
Section 33.3: Using Join in an Update
Joins can also be used in an UPDATE statement:
CREATE TABLE Users (
UserId int NOT NULL, AccountId int NOT NULL, RealName nvarchar(200) NOT NULL )
CREATE TABLE Preferences (
UserId int NOT NULL, SomeSetting bit NOT NULL )
Update the SomeSetting column of the Preferences table filtering by a predicate on the Users table as follows:
UPDATE p SET p.SomeSetting = 1 FROM Users u JOIN Preferences p ON u.UserId = p.UserId WHERE u.AccountId = 1234
p is an alias for Preferences defined in the FROM clause of the statement. Only rows with a matching AccountId from the Users table will be updated.
Update with left outer join statements
Update t SET t.Column1=100 FROM Table1 t LEFT JOIN Table12 t2 ON t2.ID=t.ID
Update tables with inner join and aggregate function
UPDATE t1 SET t1.field1 = t2.field2Sum FROM table1 t1 INNER JOIN (select field3, sum(field2) as field2Sum from table2 group by field3) as t2 on t2.field3 = t1.field3
Section 33.4: Join on a Subquery
Joining on a subquery is often used when you want to get aggregate data (such as Count, Avg, Max, or Min) from a child/details table and display that along with records from the parent/header table. For example, you may want to retrieve the top/first child row based on Date or Id or maybe you want a Count of all Child Rows or an Average.
This example uses aliases which makes queries easier to read when you have multiple tables involved. In this case we are retrieving all rows from the parent table Purchase Orders and retrieving only the last (or most recent) child row from the child table PurchaseOrderLineItems. This example assumes the child table uses incremental numeric Id's.
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SELECT po.Id, po.PODate, po.VendorName, po.Status, item.ItemNo,
item.Description, item.Cost, item.Price FROM PurchaseOrders po LEFT JOIN
(
SELECT l.PurchaseOrderId, l.ItemNo, l.Description, l.Cost, l.Price, Max(l.id) as Id FROM PurchaseOrderLineItems l GROUP BY l.PurchaseOrderId, l.ItemNo, l.Description, l.Cost, l.Price ) AS item ON item.PurchaseOrderId = po.Id
Section 33.5: Cross Join
A cross join is a Cartesian join, meaning a Cartesian product of both the tables. This join does not need any condition to join two tables. Each row in the left table will join to each row of the right table. Syntax for a cross join:
SELECT * FROM table_1 CROSS JOIN table_2
Example:
/* Sample data. */ DECLARE @Animal table (
AnimalId Int IDENTITY, Animal Varchar(20) );
DECLARE @AnimalSound table (
AnimalSoundId Int IDENTITY, AnimalId Int, Sound Varchar(20) );
INSERT INTO @Animal (Animal) VALUES ('Dog'); INSERT INTO @Animal (Animal) VALUES ('Cat'); INSERT INTO @Animal (Animal) VALUES ('Elephant');
INSERT INTO @AnimalSound (AnimalId, Sound) VALUES (1, 'Barks'); INSERT INTO @AnimalSound (AnimalId, Sound) VALUES (2, 'Meows'); INSERT INTO @AnimalSound (AnimalId, Sound) VALUES (3, 'Trumpet'); /* Sample data prepared. */
SELECT
* FROM
@Animal CROSS JOIN @AnimalSound;
Results:
AnimalId Animal AnimalSoundId AnimalId Sound ----------- -------------------- ------------- ----------- -------------------- 1 Dog 1 1 Barks 2 Cat 1 1 Barks 3 Elephant 1 1 Barks 1 Dog 2 2 Meows 2 Cat 2 2 Meows 3 Elephant 2 2 Meows 1 Dog 3 3 Trumpet 2 Cat 3 3 Trumpet
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3 Elephant 3 3 Trumpet
Note that there are other ways that a CROSS JOIN can be applied. This is a an "old style" join (deprecated since ANSI SQL-92) with no condition, which results in a cross/Cartesian join:
SELECT * FROM @Animal, @AnimalSound;
This syntax also works due to an "always true" join condition, but is not recommended and should be avoided, in favor of explicit CROSS JOIN syntax, for the sake of readability.
SELECT * FROM
@Animal JOIN @AnimalSound
ON 1=1
Section 33.6: Self Join
A table can be joined onto itself in what is known as a self join, combining records in the table with other records in the same table. Self joins are typically used in queries where a hierarchy in the table's columns is defined.
Consider the sample data in a table called Employees:
ID Name Boss_ID 1 Bob 3
2 Jim 1 3 Sam 2
Each employee's Boss_ID maps to another employee's ID. To retrieve a list of employees with their respective boss' name, the table can be joined on itself using this mapping. Note that joining a table in this manner requires the use of an alias (Bosses in this case) on the second reference to the table to distinguish itself from the original table.
SELECT Employees.Name,
Bosses.Name AS Boss FROM Employees INNER JOIN Employees AS Bosses
ON Employees.Boss_ID = Bosses.ID
Executing this query will output the following results:
Name Boss Bob Sam Jim Bob
Sam Jim
Section 33.7: Accidentally turning an outer join into an inner join
Outer joins return all the rows from one or both tables, plus matching rows.
Table People PersonID FirstName
1 Alice
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2 Bob 3 Eve
Table Scores PersonID Subject Score
1 Math 100 2 Math 54 2 Science 98
Left joining the tables:
Select * from People a left join Scores b on a.PersonID = b.PersonID
Returns:
PersonID FirstName PersonID Subject Score
1 Alice 1 Math 100 2 Bob 2 Math 54 2 Bob 2 Science 98 3 Eve NULL NULL NULL
If you wanted to return all the people, with any applicable math scores, a common mistake is to write:
Select * from People a left join Scores b on a.PersonID = b.PersonID where Subject = 'Math'
This would remove Eve from your results, in addition to removing Bob's science score, as Subject is NULL for her.
The correct syntax to remove non-Math records while retaining all individuals in the People table would be:
Select * from People a left join Scores b on a.PersonID = b.PersonID and b.Subject = 'Math'
Section 33.8: Delete using Join
Joins can also be used in a DELETE statement. Given a schema as follows:
CREATE TABLE Users (
UserId int NOT NULL, AccountId int NOT NULL, RealName nvarchar(200) NOT NULL )
CREATE TABLE Preferences (
UserId int NOT NULL, SomeSetting bit NOT NULL )
We can delete rows from the Preferences table, filtering by a predicate on the Users table as follows:
DELETE p
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FROM Users u INNER JOIN Preferences p ON u.UserId = p.UserId WHERE u.AccountId = 1234
Here p is an alias for Preferences defined in the FROM clause of the statement and we only delete rows that have a matching AccountId from the Users table.
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Chapter 34: cross apply
Section 34.1: Join table rows with dynamically generated rows from a cell
CROSS APPLY enables you to "join" rows from a table with dynamically generated rows returned by some table- value function.
Imagine that you have a Company table with a column that contains an array of products (ProductList column), and a function that parse these values and returns a set of products. You can select all rows from a Company table, apply this function on a ProductList column and "join" generated results with parent Company row:
SELECT * FROM Companies c
CROSS APPLY dbo.GetProductList( c.ProductList ) p
For each row, value of ProductList cell will be provided to the function, and the function will return those products as a set of rows that can be joined with the parent row.
Section 34.2: Join table rows with JSON array stored in cell
CROSS APPLY enables you to "join" rows from a table with collection of JSON objects stored in a column.
Imagine that you have a Company table with a column that contains an array of products (ProductList column) formatted as JSON array. OPENJSON table value function can parse these values and return the set of products. You can select all rows from a Company table, parse JSON products with OPENJSON and "join" generated results with parent Company row:
SELECT * FROM Companies c
CROSS APPLY OPENJSON( c.ProductList )
WITH ( Id int, Title nvarchar(30), Price money)
For each row, value of ProductList cell will be provided to OPENJSON function that will transform JSON objects to rows with the schema defined in WITH clause.
Section 34.3: Filter rows by array values
If you store a list of tags in a row as coma separated values, STRING_SPLIT function enables you to transform list of tags into a table of values. CROSS APPLY enables you to "join" values parsed by STRING_SPLIT function with a parent row.
Imagine that you have a Product table with a column that contains an array of comma separated tags (e.g. promo,sales,new). STRING_SPLIT and CROSS APPLY enable you to join product rows with their tags so you can filter products by tags:
SELECT * FROM Products p
CROSS APPLY STRING_SPLIT( p.Tags, ',' ) tags WHERE tags.value = 'promo'
For each row, value of Tags cell will be provided to STRING_SPLIT function that will return tag values. Then you can filter rows by these values.
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Note: STRING_SPLIT function is not available before SQL Server 2016
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Chapter 35: Computed Columns
Section 35.1: A column is computed from an expression
A computed column is computed from an expression that can use other columns in the same table. The expression can be a noncomputed column name, constant, function, and any combination of these connected by one or more operators.
Create table with a computed column
Create table NetProfit (
SalaryToEmployee int, BonusDistributed int, BusinessRunningCost int, BusinessMaintenanceCost int, BusinessEarnings int, BusinessNetIncome
As BusinessEarnings - (SalaryToEmployee + BonusDistributed + BusinessRunningCost + BusinessMaintenanceCost )
)
Value is computed and stored in the computed column automatically on inserting other values.
Insert Into NetProfit
(SalaryToEmployee, BonusDistributed, BusinessRunningCost, BusinessMaintenanceCost, BusinessEarnings) Values
(1000000,
10000, 1000000, 50000, 2500000)
Section 35.2: Simple example we normally use in log tables
CREATE TABLE [dbo].[ProcessLog]( [LogId] [int] IDENTITY(1,1) NOT NULL, [LogType] [varchar](20) NULL, [StartTime] [datetime] NULL, [EndTime] [datetime] NULL, [RunMinutes] AS (datediff(minute,coalesce([StartTime],getdate()),coalesce([EndTime],getdate())))
This gives run difference in minutes for runtime which will be very handy..
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Chapter 36: Common Table Expressions
Section 36.1: Generate a table of dates using CTE
DECLARE @startdate CHAR(8), @numberDays TINYINT
SET @startdate = '20160101' SET @numberDays = 10;
WITH CTE_DatesTable AS (
SELECT CAST(@startdate as date) AS [date] UNION ALL SELECT DATEADD(dd, 1, [date]) FROM CTE_DatesTable WHERE DATEADD(dd, 1, [date]) <= DateAdd(DAY, @numberDays-1, @startdate) )
SELECT [date] FROM CTE_DatesTable
OPTION (MAXRECURSION 0)
This example returns a single-column table of dates, starting with the date specified in the @startdate variable, and returning the next @numberDays worth of dates.
Section 36.2: Employee Hierarchy
Table Setup
CREATE TABLE dbo.Employees (
EmployeeID INT NOT NULL PRIMARY KEY, FirstName NVARCHAR(50) NOT NULL, LastName NVARCHAR(50) NOT NULL, ManagerID INT NULL )
GO
INSERT INTO Employees VALUES (101, 'Ken', 'Sánchez', NULL) INSERT INTO Employees VALUES (102, 'Keith', 'Hall', 101) INSERT INTO Employees VALUES (103, 'Fred', 'Bloggs', 101) INSERT INTO Employees VALUES (104, 'Joseph', 'Walker', 102) INSERT INTO Employees VALUES (105, 'Žydrė', 'Klybė', 101) INSERT INTO Employees VALUES (106, 'Sam', 'Jackson', 105) INSERT INTO Employees VALUES (107, 'Peter', 'Miller', 103) INSERT INTO Employees VALUES (108, 'Chloe', 'Samuels', 105) INSERT INTO Employees VALUES (109, 'George', 'Weasley', 105) INSERT INTO Employees VALUES (110, 'Michael', 'Kensington', 106)
Common Table Expression
;WITH cteReports (EmpID, FirstName, LastName, SupervisorID, EmpLevel) AS (
SELECT EmployeeID, FirstName, LastName, ManagerID, 1 FROM Employees WHERE ManagerID IS NULL
UNION ALL
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SELECT e.EmployeeID, e.FirstName, e.LastName, e.ManagerID, r.EmpLevel + 1 FROM Employees AS e INNER JOIN cteReports AS r ON e.ManagerID = r.EmpID )
SELECT
FirstName + ' ' + LastName AS FullName, EmpLevel, (SELECT FirstName + ' ' + LastName FROM Employees WHERE EmployeeID = cteReports.SupervisorID) AS ManagerName FROM cteReports ORDER BY EmpLevel, SupervisorID
Output:
FullName EmpLevel ManagerName Ken Sánchez 1 null
Keith Hall 2 Ken Sánchez
Fred Bloggs 2 Ken Sánchez
Žydre Klybe 2 Ken Sánchez
Joseph Walker 3 Keith Hall
Peter Miller 3 Fred Bloggs
Sam Jackson 3 Žydre Klybe
Chloe Samuels 3 Žydre Klybe
George Weasley 3 Žydre Klybe
Michael Kensington 4 Sam Jackson
Section 36.3: Recursive CTE
This example shows how to get every year from this year to 2011 (2012 - 1).
WITH yearsAgo (
myYear ) AS (
-- Base Case: This is where the recursion starts SELECT DATEPART(year, GETDATE()) AS myYear
UNION ALL -- This MUST be UNION ALL (cannot be UNION)
-- Recursive Section: This is what we're doing with the recursive call SELECT yearsAgo.myYear - 1 FROM yearsAgo WHERE yearsAgo.myYear >= 2012 )
SELECT myYear FROM yearsAgo; -- A single SELECT, INSERT, UPDATE, or DELETE
myYear 2016
2015
2014 2013
2012
2011
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You can control the recursion (think stack overflow in code) with MAXRECURSION as a query option that will limit the number of recursive calls.
WITH yearsAgo (
myYear ) AS (
-- Base Case SELECT DATEPART(year , GETDATE()) AS myYear UNION ALL -- Recursive Section SELECT yearsAgo.myYear - 1 FROM yearsAgo WHERE yearsAgo.myYear >= 2002 )
SELECT * FROM yearsAgo OPTION (MAXRECURSION 10);
Msg 530, Level 16, State 1, Line 2The statement terminated. The maximum recursion 10 has been exhausted before statement completion.
Section 36.4: Delete duplicate rows using CTE
Employees table :
| ID | FirstName | LastName | Gender | Salary | +------+-----------+----------+--------+--------+ | 1 | Mark | Hastings | Male | 60000 | | 1 | Mark | Hastings | Male | 60000 | | 2 | Mary | Lambeth | Female | 30000 | | 2 | Mary | Lambeth | Female | 30000 | | 3 | Ben | Hoskins | Male | 70000 | | 3 | Ben | Hoskins | Male | 70000 | | 3 | Ben | Hoskins | Male | 70000 | +------+-----------+----------+--------+--------+
CTE (Common Table Expression) :
WITH EmployeesCTE AS (
SELECT *, ROW_NUMBER()OVER(PARTITION BY ID ORDER BY ID) AS RowNumber FROM Employees ) DELETE FROM EmployeesCTE WHERE RowNumber > 1
Execution result :
| ID | FirstName | LastName | Gender | Salary | +------+-----------+----------+--------+--------+ | 1 | Mark | Hastings | Male | 60000 | | 2 | Mary | Lambeth | Female | 30000 | | 3 | Ben | Hoskins | Male | 70000 | +------+-----------+----------+--------+--------+
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Section 36.5: CTE with multiple AS statements
;WITH cte_query_1 AS (
SELECT * FROM database.table1 ), cte_query_2 AS (
SELECT * FROM database.table2 ) SELECT * FROM cte_query_1 WHERE cte_query_one.fk IN (
SELECT PK FROM cte_query_2 )
With common table expressions, it is possible to create multiple queries using comma-separated AS statements. A query can then reference any or all of those queries in many different ways, even joining them.
Section 36.6: Find nth highest salary using CTE
Employees table :
| ID | FirstName | LastName | Gender | Salary | +------+-----------+----------+--------+--------+ | 1 | Jahangir | Alam | Male | 70000 | | 2 | Arifur | Rahman | Male | 60000 | | 3 | Oli | Ahammed | Male | 45000 | | 4 | Sima | Sultana | Female | 70000 | | 5 | Sudeepta | Roy | Male | 80000 | +------+-----------+----------+--------+--------+
CTE (Common Table Expression) :
WITH RESULT AS (
SELECT SALARY,
DENSE_RANK() OVER (ORDER BY SALARY DESC) AS DENSERANK FROM EMPLOYEES ) SELECT TOP 1 SALARY FROM RESULT WHERE DENSERANK = 1
To find 2nd highest salary simply replace N with 2. Similarly, to find 3rd highest salary, simply replace N with 3.
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Chapter 37: Move and copy data around tables
Section 37.1: Copy data from one table to another
This code selects data out of a table and displays it in the query tool (usually SSMS)
SELECT Column1, Column2, Column3 FROM MySourceTable;
This code inserts that data into a table:
INSERT INTO MyTargetTable (Column1, Column2, Column3) SELECT Column1, Column2, Column3 FROM MySourceTable;
Section 37.2: Copy data into a table, creating that table on the fly
This code selects data out of a table:
SELECT Column1, Column2, Column3 FROM MySourceTable;
This code creates a new table called MyNewTable and puts that data into it
SELECT Column1, Column2, Column3 INTO MyNewTable FROM MySourceTable;
Section 37.3: Move data into a table (assuming unique keys method)
To move data you first insert it into the target, then delete whatever you inserted from the source table. This is not a normal SQL operation but it may be enlightening
What did you insert? Normally in databases you need to have one or more columns that you can use to uniquely identify rows so we will assume that and make use of it.
This statement selects some rows
SELECT Key1, Key2, Column3, Column4 FROM MyTable;
First we insert these into our target table:
INSERT INTO TargetTable (Key1, Key2, Column3, Column4) SELECT Key1, Key2, Column3, Column4 FROM MyTable;
Now assuming records in both tables are unique on Key1,Key2, we can use that to find and delete data out of the source table
DELETE MyTable WHERE EXISTS (
SELECT * FROM TargetTable WHERE TargetTable.Key1 = SourceTable.Key1
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AND TargetTable.Key2 = SourceTable.Key2 );
This will only work correctly if Key1, Key2 are unique in both tables
Lastly, we don't want the job half done. If we wrap this up in a transaction then either all data will be moved, or nothing will happen. This ensures we don't insert the data in then find ourselves unable to delete the data out of the source.
BEGIN TRAN;
INSERT INTO TargetTable (Key1, Key2, Column3, Column4) SELECT Key1, Key2, Column3, Column4 FROM MyTable;
DELETE MyTable WHERE EXISTS (
SELECT * FROM TargetTable WHERE TargetTable.Key1 = SourceTable.Key1 AND TargetTable.Key2 = SourceTable.Key2 );
COMMIT TRAN;
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Chapter 38: Limit Result Set
Parameter Details TOP Limiting keyword. Use with a number.
PERCENT Percentage keyword. Comes after TOP and limiting number.
As database tables grow, it's often useful to limit the results of queries to a fixed number or percentage. This can be achieved using SQL Server's TOP keyword or OFFSET FETCH clause.
Section 38.1: Limiting With PERCENT
This example limits SELECT result to 15 percentage of total row count.
SELECT TOP 15 PERCENT * FROM table_name
Section 38.2: Limiting with FETCH
Version ≥ SQL Server 2012
FETCH is generally more useful for pagination, but can be used as an alternative to TOP:
SELECT * FROM table_name ORDER BY 1 OFFSET 0 ROWS FETCH NEXT 50 ROWS ONLY
Section 38.3: Limiting With TOP
This example limits SELECT result to 100 rows.
SELECT TOP 100 * FROM table_name;
It is also possible to use a variable to specify the number of rows:
DECLARE @CountDesiredRows int = 100; SELECT TOP (@CountDesiredRows) * FROM table_name;
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Chapter 39: Retrieve Information about your Instance
Section 39.1: General Information about Databases, Tables, Stored procedures and how to search them
Query to search last executed sp's in db
SELECT execquery.last_execution_time AS [Date Time], execsql.text AS [Script] FROM sys.dm_exec_query_stats AS execquery CROSS APPLY sys.dm_exec_sql_text(execquery.sql_handle) AS execsql ORDER BY execquery.last_execution_time DESC
Query to search through Stored procedures
SELECT o.type_desc AS ROUTINE_TYPE,o.[name] AS ROUTINE_NAME, m.definition AS ROUTINE_DEFINITION FROM sys.sql_modules AS m INNER JOIN sys.objects AS o ON m.object_id = o.object_id WHERE m.definition LIKE '%Keyword%' order by ROUTINE_NAME
Query to Find Column From All Tables of Database
SELECT t.name AS table_name, SCHEMA_NAME(schema_id) AS schema_name, c.name AS column_name FROM sys.tables AS t INNER JOIN sys.columns c ON t.OBJECT_ID = c.OBJECT_ID where c.name like 'Keyword%' ORDER BY schema_name, table_name;
Query to to check restore details
WITH LastRestores AS ( SELECT
DatabaseName = [d].[name] , [d].[create_date] , [d].[compatibility_level] , [d].[collation_name] , r.*, RowNum = ROW_NUMBER() OVER (PARTITION BY d.Name ORDER BY r.[restore_date] DESC) FROM master.sys.databases d LEFT OUTER JOIN msdb.dbo.[restorehistory] r ON r.[destination_database_name] = d.Name ) SELECT * FROM [LastRestores] WHERE [RowNum] = 1
Query to to find the log
select top 100 * from databaselog Order by Posttime desc
Query to to check the Sps details
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SELECT name, create_date, modify_date FROM sys.objects WHERE type = 'P' Order by modify_date desc
Section 39.2: Get information on current sessions and query executions
sp_who2
This procedure can be used to find information on current SQL server sessions. Since it is a procedure, it's often helpful to store the results into a temporary table or table variable so one can order, filter, and transform the results as needed.
The below can be used for a queryable version of sp_who2:
-- Create a variable table to hold the results of sp_who2 for querying purposes
DECLARE @who2 TABLE (
SPID INT NULL, Status VARCHAR(1000) NULL, Login SYSNAME NULL, HostName SYSNAME NULL, BlkBy SYSNAME NULL, DBName SYSNAME NULL, Command VARCHAR(8000) NULL, CPUTime INT NULL, DiskIO INT NULL, LastBatch VARCHAR(250) NULL, ProgramName VARCHAR(250) NULL, SPID2 INT NULL, -- a second SPID for some reason...? REQUESTID INT NULL )
INSERT INTO @who2 EXEC sp_who2
SELECT * FROM @who2 w WHERE 1=1
Examples:
-- Find specific user sessions: SELECT * FROM @who2 w WHERE 1=1
and login = 'userName'
-- Find longest CPUTime queries: SELECT top 5 * FROM @who2 w WHERE 1=1 order by CPUTime desc
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Section 39.3: Information about SQL Server version
To discover SQL Server's edition, product level and version number as well as the host machine name and the server type:
SELECT SERVERPROPERTY('MachineName') AS Host,
SERVERPROPERTY('InstanceName') AS Instance, DB_NAME() AS DatabaseContext, SERVERPROPERTY('Edition') AS Edition, SERVERPROPERTY('ProductLevel') AS ProductLevel, CASE SERVERPROPERTY('IsClustered')
WHEN 1 THEN 'CLUSTERED' ELSE 'STANDALONE' END AS ServerType, @@VERSION AS VersionNumber;
Section 39.4: Retrieve Edition and Version of Instance
SELECT SERVERPROPERTY('ProductVersion') AS ProductVersion,
SERVERPROPERTY('ProductLevel') AS ProductLevel, SERVERPROPERTY('Edition') AS Edition, SERVERPROPERTY('EngineEdition') AS EngineEdition;
Section 39.5: Retrieve Instance Uptime in Days
SELECT DATEDIFF(DAY, login_time, getdate()) UpDays FROM master..sysprocesses WHERE spid = 1
Section 39.6: Retrieve Local and Remote Servers
To retrieve a list of all servers registered on the instance:
EXEC sp_helpserver;
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Chapter 40: With Ties Option
Section 40.1: Test Data
CREATE TABLE #TEST ( Id INT, Name VARCHAR(10) )
Insert Into #Test select 1,'A' Union All Select 1,'B' union all Select 1,'C' union all Select 2,'D'
Below is the output of above table,As you can see Id Column is repeated three times..
Id Name 1 A 1 B 1 C 2 D
Now Lets check the output using simple order by..
Select Top (1) Id,Name From #test Order By Id ;
Output :(Output of above query is not guaranteed to be same every time )
Id Name 1 B
Lets run the Same query With Ties Option..
Select Top (1) With Ties Id,Name
From #test Order By Id
Output :
Id Name 1 A 1 B 1 C
As you can see SQL Server outputs all the Rows which are tied with Order by Column. Lets see one more Example to understand this better..
Select Top (1) With Ties Id,Name
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From #test Order By Id ,Name
Output:
Id Name 1 A
In Summary ,when we use with Ties Option,SQL Server Outputs all the Tied rows irrespective of limit we impose
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Chapter 41: String Functions
Section 41.1: Quotename
Returns a Unicode string surrounded by delimiters to make it a valid SQL Server delimited identifier.
Parameters:
character string. A string of Unicode data, up to 128 characters (sysname). If an input string is longer than 128 1.
characters function returns null. quote character. Optional. A single character to use as a delimiter. Can be a single quotation mark (' or ``), 2.
a left or right bracket ({,[,(,< or >,),],}) or a double quotation mark ("). Any other value will return null. Default value is square brackets.
SELECT QUOTENAME('what''s my name?') -- Returns [what's my name?]
SELECT QUOTENAME('what''s my name?', '[') -- Returns [what's my name?] SELECT QUOTENAME('what''s my name?', ']') -- Returns [what's my name?]
SELECT QUOTENAME('what''s my name?', '''') -- Returns 'what''s my name?'
SELECT QUOTENAME('what''s my name?', '"') -- Returns "what's my name?"
SELECT QUOTENAME('what''s my name?', ')') -- Returns (what's my name?) SELECT QUOTENAME('what''s my name?', '(') -- Returns (what's my name?)
SELECT QUOTENAME('what''s my name?', '<') -- Returns <what's my name?> SELECT QUOTENAME('what''s my name?', '>') -- Returns <what's my name?>
SELECT QUOTENAME('what''s my name?', '{') -- Returns {what's my name?} SELECT QUOTENAME('what''s my name?', '}') -- Returns {what's my name?}
SELECT QUOTENAME('what''s my name?', '`') -- Returns `what's my name?`
Section 41.2: Replace
Returns a string (varchar or nvarchar) where all occurrences of a specified sub string is replaced with another sub string.
Parameters:
string expression. This is the string that would be searched. It can be a character or binary data type. 1. pattern. This is the sub string that would be replaced. It can be a character or binary data type. The pattern 2.
argument cannot be an empty string. replacement. This is the sub string that would replace the pattern sub string. It can be a character or binary 3.
data.
SELECT REPLACE('This is my string', 'is', 'XX') -- Returns 'ThXX XX my string'.
Notes:
If string expression is not of type varchar(max) or nvarchar(max), the replace function truncates the return value at 8,000 chars. Return data type depends on input data types - returns nvarchar if one of the input values is nvarchar, or varchar otherwise.
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Return NULL if any of the input parameters is NULL
Section 41.3: Substring
Returns a substring that starts with the char that's in the specified start index and the specified max length.
Parameters:
Character expression. The character expression can be of any data type that can be implicitly converted to 1.
varchar or nvarchar, except for text or ntext. Start index. A number (int or bigint) that specifies the start index of the requested substring. (Note: strings 2. in sql server are base 1 index, meaning that the first character of the string is index 1). This number can be less then 1. In this case, If the sum of start index and max length is greater then 0, the return string would be a string starting from the first char of the character expression and with the length of (start index + max length - 1). If it's less then 0, an empty string would be returned. Max length. An integer number between 0 and bigint max value (9,223,372,036,854,775,807). If the max 3.
length parameter is negative, an error will be raised.
SELECT SUBSTRING('This is my string', 6, 5) -- returns 'is my'
If the max length + start index is more then the number of characters in the string, the entier string is returned.
SELECT SUBSTRING('Hello World',1,100) -- returns 'Hello World'
If the start index is bigger then the number of characters in the string, an empty string is returned.
SELECT SUBSTRING('Hello World',15,10) -- returns ''
Section 41.4: String_Split
Version ≥ SQL Server 2016
Splits a string expression using a character separator. Note that STRING_SPLIT() is a table-valued function and therefore must be used within FROM clause.
Parameters:
string. Any character type expression (char, nchar, varchar or nvarchar) 1. seperator. A single character expression of any type (char(1), nchar(1), varchar(1) or nvarchar(1)). 2.
Returns a single column table where each row contains a fragment of the string. The name of the columns is value, and the datatype is nvarchar if any of the parameters is either nchar or nvarchar, otherwise varchar.
The following example splits a string using space as a separator:
SELECT value FROM STRING_SPLIT('Lorem ipsum dolor sit amet.', ' ');
Result:
value ----- Lorem ipsum dolor sit
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amet.
Remarks:
The STRING_SPLIT function is available only under compatibility level 130. If your database compatibility level is lower than 130, SQL Server will not be able to find and execute STRING_SPLIT function. You can change the compatibility level of a database using the following command:
ALTER DATABASE [database_name] SET COMPATIBILITY_LEVEL = 130
Version < SQL Server 2016
Older versions of sql server does not have a built in split string function. There are many user defined functions that handles the problem of splitting a string. You can read Aaron Bertrand's article Split strings the right way – or the next best way for a comprehensive comparison of some of them.
Section 41.5: Left
Returns a sub string starting with the left most char of a string and up to the maximum length specified.
Parameters:
character expression. The character expression can be of any data type that can be implicitly converted to 1.
varchar or nvarchar, except for text or ntext max length. An integer number between 0 and bigint max value (9,223,372,036,854,775,807). 2.
If the max length parameter is negative, an error will be raised.
SELECT LEFT('This is my string', 4) -- result: 'This'
If the max length is more then the number of characters in the string, the entier string is returned.
SELECT LEFT('This is my string', 50) -- result: 'This is my string'
Section 41.6: Right
Returns a sub string that is the right most part of the string, with the specified max length.
Parameters:
character expression. The character expression can be of any data type that can be implicitly converted to 1.
varchar or nvarchar, except for text or ntext max length. An integer number between 0 and bigint max value (9,223,372,036,854,775,807). If the max 2.
length parameter is negative, an error will be raised.
SELECT RIGHT('This is my string', 6) -- returns 'string'
If the max length is more then the number of characters in the string, the entier string is returned.
SELECT RIGHT('This is my string', 50) -- returns 'This is my string'
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Section 41.7: Soundex
Returns a four-character code (varchar) to evaluate the phonetic similarity of two strings.
Parameters:
character expression. An alphanumeric expression of character data. 1.
The soundex function creates a four-character code that is based on how the character expression would sound when spoken. the first char is the the upper case version of the first character of the parameter, the rest 3 characters are numbers representing the letters in the expression (except a, e, i, o, u, h, w and y that are ignored).
SELECT SOUNDEX ('Smith') -- Returns 'S530'
SELECT SOUNDEX ('Smythe') -- Returns 'S530'
Section 41.8: Format
Version ≥ SQL Server 2012
Returns a NVARCHAR value formatted with the specified format and culture (if specified). This is primarily used for converting date-time types to strings.
Parameters:
value. An expression of a supported data type to format. valid types are listed below. 1. format. An NVARCHAR format pattern. See Microsoft official documentation for standard and custom format 2.
strings. culture. Optional. nvarchar argument specifying a culture. The default value is the culture of the current 3.
session.
DATE
Using standard format strings:
DECLARE @d DATETIME = '2016-07-31';
SELECT
FORMAT ( @d, 'd', 'en-US' ) AS 'US English Result' -- Returns '7/31/2016' ,FORMAT ( @d, 'd', 'en-gb' ) AS 'Great Britain English Result' -- Returns '31/07/2016' ,FORMAT ( @d, 'd', 'de-de' ) AS 'German Result' -- Returns '31.07.2016' ,FORMAT ( @d, 'd', 'zh-cn' ) AS 'Simplified Chinese (PRC) Result' -- Returns '2016/7/31' ,FORMAT ( @d, 'D', 'en-US' ) AS 'US English Result' -- Returns 'Sunday, July 31, 2016' ,FORMAT ( @d, 'D', 'en-gb' ) AS 'Great Britain English Result' -- Returns '31 July 2016' ,FORMAT ( @d, 'D', 'de-de' ) AS 'German Result' -- Returns 'Sonntag, 31. Juli 2016'
Using custom format strings:
SELECT FORMAT( @d, 'dd/MM/yyyy', 'en-US' ) AS 'DateTime Result' -- Returns '31/07/2016'
,FORMAT(123456789,'###-##-####') AS 'Custom Number Result' -- Returns '123-45-6789', ,FORMAT( @d,'dddd, MMMM dd, yyyy hh:mm:ss tt','en-US') AS 'US' -- Returns 'Sunday, July 31, 2016 12:00:00 AM'
,FORMAT( @d,'dddd, MMMM dd, yyyy hh:mm:ss tt','hi-IN') AS 'Hindi' -- Returns रवि◌व◌ार, ज◌ल◌ाई 31, 2016 12:00:00 प◌र◌व◌ाह◌
,FORMAT ( @d, 'dddd', 'en-US' ) AS 'US' -- Returns 'Sunday' ,FORMAT ( @d, 'dddd', 'hi-IN' ) AS 'Hindi' -- Returns 'रवि◌व◌ार'
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FORMAT can also be used for formatting CURRENCY,PERCENTAGE and NUMBERS.
CURRENCY
DECLARE @Price1 INT = 40 SELECT FORMAT(@Price1,'c','en-US') AS 'CURRENCY IN US Culture' -- Returns '$40.00'
,FORMAT(@Price1,'c','de-DE') AS 'CURRENCY IN GERMAN Culture' -- Returns '40,00 €'
We can specify the number of digits after the decimal.
DECLARE @Price DECIMAL(5,3) = 40.356 SELECT FORMAT( @Price, 'C') AS 'Default', -- Returns '$40.36'
FORMAT( @Price, 'C0') AS 'With 0 Decimal', -- Returns '$40' FORMAT( @Price, 'C1') AS 'With 1 Decimal', -- Returns '$40.4' FORMAT( @Price, 'C2') AS 'With 2 Decimal', -- Returns '$40.36'
PERCENTAGE
DECLARE @Percentage float = 0.35674 SELECT FORMAT( @Percentage, 'P') AS '% Default', -- Returns '35.67 %' FORMAT( @Percentage, 'P0') AS '% With 0 Decimal', -- Returns '36 %' FORMAT( @Percentage, 'P1') AS '% with 1 Decimal' -- Returns '35.7 %'
NUMBER
DECLARE @Number AS DECIMAL(10,2) = 454545.389 SELECT FORMAT( @Number, 'N','en-US') AS 'Number Format in US', -- Returns '454,545.39' FORMAT( @Number, 'N','en-IN') AS 'Number Format in INDIA', -- Returns '4,54,545.39' FORMAT( @Number, '#.0') AS 'With 1 Decimal', -- Returns '454545.4' FORMAT( @Number, '#.00') AS 'With 2 Decimal', -- Returns '454545.39' FORMAT( @Number, '#,##.00') AS 'With Comma and 2 Decimal', -- Returns '454,545.39' FORMAT( @Number, '##.00') AS 'Without Comma and 2 Decimal', -- Returns '454545.39' FORMAT( @Number, '000000000') AS 'Left-padded to nine digits' -- Returns '000454545'
Valid value types list: (source)
Category Type .Net type ------------------------------------------- Numeric bigint Int64 Numeric int Int32 Numeric smallint Int16 Numeric tinyint Byte Numeric decimal SqlDecimal Numeric numeric SqlDecimal Numeric float Double Numeric real Single Numeric smallmoney Decimal Numeric money Decimal Date and Time date DateTime Date and Time time TimeSpan Date and Time datetime DateTime Date and Time smalldatetime DateTime Date and Time datetime2 DateTime Date and Time datetimeoffset DateTimeOffset
Important Notes:
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FORMAT returns NULL for errors other than a culture that is not valid. For example, NULL is returned if the value specified in format is not valid. FORMAT relies on the presence of the .NET Framework Common Language Runtime (CLR). FORMAT relies upon CLR formatting rules which dictate that colons and periods must be escaped. Therefore, when the format string (second parameter) contains a colon or period, the colon or period must be escaped with backslash when an input value (first parameter) is of the time data type.
See also Date & Time Formatting using FORMAT documentation example.
Section 41.9: String_escape
Version ≥ SQL Server 2016
Escapes special characters in texts and returns text (nvarchar(max)) with escaped characters.
Parameters:
text. is a nvarchar expression representing the string that should be escaped. 1.
type. Escaping rules that will be applied. Currently the only supported value is 'json'. 2.
SELECT STRING_ESCAPE('\ / \\ " ', 'json') -- returns '\\\t\/\n\\\\\t\"\t'
List of characters that will be escaped:
Special character Encoded sequence ------------------------------------- Quotation mark (") \" Reverse solidus (\) \\ Solidus (/) \/ Backspace \b Form feed \f New line \n Carriage return \r Horizontal tab \t
Control character Encoded sequence ------------------------------------ CHAR(0) \u0000 CHAR(1) \u0001 ... ... CHAR(31) \u001f
Section 41.10: ASCII
Returns an int value representing the ASCII code of the leftmost character of a string.
SELECT ASCII('t') -- Returns 116 SELECT ASCII('T') -- Returns 84 SELECT ASCII('This') -- Returns 84
If the string is Unicode and the leftmost character is not ASCII but representable in the current collation, a value greater than 127 can be returned:
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SELECT ASCII(N'ï') -- returns 239 when `SERVERPROPERTY('COLLATION') = 'SQL_Latin1_General_CP1_CI_AS'`
If the string is Unicode and the leftmost character cannot be represented in the current collation, the int value of 63 is returned: (which represents question mark in ASCII):
SELECT ASCII(N' ') -- returns 63 SELECT ASCII(nchar(2039)) -- returns 63
Section 41.11: Char
Returns a char represented by an int ASCII code.
SELECT CHAR(116) -- Returns 't' SELECT CHAR(84) -- Returns 'T'
This can be used to introduce new line/line feed CHAR(10), carriage returns CHAR(13), etc. See AsciiTable.com for reference.
If the argument value is not between 0 and 255, the CHAR function returns NULL. The return data type of the CHAR function is char(1)
Section 41.12: Concat
Version ≥ SQL Server 2012
Returns a string that is the result of two or more strings joined together. CONCAT accepts two or more arguments.
SELECT CONCAT('This', ' is', ' my', ' string') -- returns 'This is my string'
Note: Unlike concatenating strings using the string concatenation operator (+), when passing a null value to the concat function it will implicitly convert it to an empty string:
SELECT CONCAT('This', NULL, ' is', ' my', ' string'), -- returns 'This is my string'
'This' + NULL + ' is' + ' my' + ' string' -- returns NULL.
Also arguments of a non-string type will be implicitly converted to a string:
SELECT CONCAT('This', ' is my ', 3, 'rd string') -- returns 'This is my 3rd string'
Non-string type variables will also be converted to string format, no need to manually covert or cast it to string:
DECLARE @Age INT=23; SELECT CONCAT('Ram is ', @Age,' years old'); -- returns 'Ram is 23 years old'
Version < SQL Server 2012
Older versions do not support CONCAT function and must use the string concatenation operator (+) instead. Non- string types must be cast or converted to string types in order to concatenate them this way.
SELECT 'This is the number ' + CAST(42 AS VARCHAR(5)) --returns 'This is the number 42'
Section 41.13: LTrim
Returns a character expression (varchar or nvarchar) after removing all leading white spaces, i.e., white spaces
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from the left through to the first non-white space character.
Parameters:
character expression. Any expression of character or binary data that can be implicitly converted to varcher, 1.
except text, ntext and image.
SELECT LTRIM(' This is my string') -- Returns 'This is my string'
Section 41.14: RTrim
Returns a character expression (varchar or nvarchar) after removing all trailing white spaces, i.e., spaces from the right end of the string up until the first non-white space character to the left.
Parameters:
character expression. Any expression of character or binary data that can be implicitly converted to varcher, 1.
except text, ntext and image.
SELECT RTRIM('This is my string ') -- Returns 'This is my string'
Section 41.15: PatIndex
Returns the starting position of the first occurrence of a the specified pattern in the specified expression.
Parameters:
pattern. A character expression the contains the sequence to be found. Limited to A maximum length of 1.
8000 chars. Wildcards (%, _) can be used in the pattern. If the pattern does not start with a wildcard, it may only match whatever is in the beginning of the expression. If it doesn't end with a wildcard, it may only match whatever is in the end of the expression.
expression. Any string data type. 2.
SELECT PATINDEX('%ter%', 'interesting') -- Returns 3.
SELECT PATINDEX('%t_r%t%', 'interesting') -- Returns 3.
SELECT PATINDEX('ter%', 'interesting') -- Returns 0, since 'ter' is not at the start.
SELECT PATINDEX('inter%', 'interesting') -- Returns 1.
SELECT PATINDEX('%ing', 'interesting') -- Returns 9.
Section 41.16: Space
Returns a string (varchar) of repeated spaces.
Parameters:
integer expression. Any integer expression, up to 8000. If negative, null is returned. if 0, an empty string is 1.
returned. (To return a string longer then 8000 spaces, use Replicate.
SELECT SPACE(-1) -- Returns NULL SELECT SPACE(0) -- Returns an empty string
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SELECT SPACE(3) -- Returns ' ' (a string containing 3 spaces)
Section 41.17: Dierence
Returns an integer (int) value that indicates the difference between the soundex values of two character expressions.
Parameters:
character expression 1. 1. character expression 2. 2.
Both parameters are alphanumeric expressions of character data.
The integer returned is the number of chars in the soundex values of the parameters that are the same, so 4 means that the expressions are very similar and 0 means that they are very different.
SELECT SOUNDEX('Green'), -- G650
SOUNDEX('Greene'), -- G650 DIFFERENCE('Green','Greene') -- Returns 4
SELECT SOUNDEX('Blotchet-Halls'), -- B432 SOUNDEX('Greene'), -- G650 DIFFERENCE('Blotchet-Halls', 'Greene') -- Returns 0
Section 41.18: Len
Returns the number of characters of a string. Note: the LEN function ignores trailing spaces:
SELECT LEN('My string'), -- returns 9
LEN('My string '), -- returns 9 LEN(' My string') -- returns 12
If the length including trailing spaces is desired there are several techniques to achieve this, although each has its drawbacks. One technique is to append a single character to the string, and then use the LEN minus one:
DECLARE @str varchar(100) = 'My string ' SELECT LEN(@str + 'x') - 1 -- returns 12
The drawback to this is if the type of the string variable or column is of the maximum length, the append of the extra character is discarded, and the resulting length will still not count trailing spaces. To address that, the following modified version solves the problem, and gives the correct results in all cases at the expense of a small amount of additional execution time, and because of this (correct results, including with surrogate pairs, and reasonable execution speed) appears to be the best technique to use:
SELECT LEN(CONVERT(NVARCHAR(MAX), @str) + 'x') - 1
Another technique is to use theDATALENGTH function.
DECLARE @str varchar(100) = 'My string ' SELECT DATALENGTH(@str) -- returns 12
It's important to note though that DATALENGTH returns the length in bytes of the string in memory. This will be different for varchar vs. nvarchar.
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DECLARE @str nvarchar(100) = 'My string ' SELECT DATALENGTH(@str) -- returns 24
You can adjust for this by dividing the datalength of the string by the datalength of a single character (which must be of the same type). The example below does this, and also handles the case where the target string happens to be empty, thus avoiding a divide by zero.
DECLARE @str nvarchar(100) = 'My string ' SELECT DATALENGTH(@str) / DATALENGTH(LEFT(LEFT(@str, 1) + 'x', 1)) -- returns 12
Even this, though, has a problem in SQL Server 2012 and above. It will produce incorrect results when the string contains surrogate pairs (some characters can occupy more bytes than other characters in the same string).
Another technique is to use REPLACE to convert spaces to a non-space character, and take the LEN of the result. This gives correct results in all cases, but has very poor execution speed with long strings.
Section 41.19: Lower
Returns a character expression (varchar or nvarchar) after converting all uppercase characters to lowercase.
Parameters:
Character expression. Any expression of character or binary data that can be implicitly converted to varchar. 1.
SELECT LOWER('This IS my STRING') -- Returns 'this is my string'
DECLARE @String nchar(17) = N'This IS my STRING'; SELECT LOWER(@String) -- Returns 'this is my string'
Section 41.20: Upper
Returns a character expression (varchar or nvarchar) after converting all lowercase characters to uppercase.
Parameters:
Character expression. Any expression of character or binary data that can be implicitly converted to varchar. 1.
SELECT UPPER('This IS my STRING') -- Returns 'THIS IS MY STRING'
DECLARE @String nchar(17) = N'This IS my STRING'; SELECT UPPER(@String) -- Returns 'THIS IS MY STRING'
Section 41.21: Unicode
Returns the integer value representing the Unicode value of the first character of the input expression.
Parameters:
Unicode character expression. Any valid nchar or nvarchar expression. 1.
SELECT UNICODE(N'Ɛ') -- Returns 400
DECLARE @Unicode nvarchar(11) = N'Ɛ is a char' SELECT UNICODE(@Unicode) -- Returns 400
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Section 41.22: NChar
Returns the Unicode character(s) (nchar(1) or nvarchar(2)) corresponding to the integer argument it receives, as defined by the Unicode standard.
Parameters:
integer expression. Any integer expression that is a positive number between 0 and 65535, or if the collation 1. of the database supports supplementary character (CS) flag, the supported range is between 0 to 1114111. If the integer expression does not fall inside this range, null is returned.
SELECT NCHAR(257) -- Returns 'ā' SELECT NCHAR(400) -- Returns 'Ɛ'
Section 41.23: Str
Returns character data (varchar) converted from numeric data.
Parameters:
float expression. An approximate numeric data type with a decimal point. 1. length. optional. The total length of the string expression that would return, including digits, decimal point 2.
and leading spaces (if needed). The default value is 10. decimal. optional. The number of digits to the right of the decimal point. If higher then 16, the result would 3.
be truncated to sixteen places to the right of the decimal point.
SELECT STR(1.2) -- Returns ' 1'
SELECT STR(1.2, 3) -- Returns ' 1'
SELECT STR(1.2, 3, 2) -- Returns '1.2'
SELECT STR(1.2, 5, 2) -- Returns ' 1.20'
SELECT STR(1.2, 5, 5) -- Returns '1.200'
SELECT STR(1, 5, 2) -- Returns ' 1.00'
SELECT STR(1) -- Returns ' 1'
Section 41.24: Reverse
Returns a string value in reversed order.
Parameters:
string expression. Any string or binary data that can be implicitly converted to varchar. 1.
Select REVERSE('Sql Server') -- Returns 'revreS lqS'
Section 41.25: Replicate
Repeats a string value a specified number of times.
Parameters:
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string expression. String expression can be a character string or binary data. 1. integer expression. Any integer type, including bigint. If negative, null is returned. If 0, an empty string is 2.
returned.
SELECT REPLICATE('a', -1) -- Returns NULL
SELECT REPLICATE('a', 0) -- Returns ''
SELECT REPLICATE('a', 5) -- Returns 'aaaaa'
SELECT REPLICATE('Abc', 3) -- Returns 'AbcAbcAbc'
Note: If string expression is not of type varchar(max) or nvarchar(max), the return value will not exceed 8000 chars. Replicate will stop before adding the string that will cause the return value to exceed that limit:
SELECT LEN(REPLICATE('a b c d e f g h i j k l', 350)) -- Returns 7981
SELECT LEN(REPLICATE(cast('a b c d e f g h i j k l' as varchar(max)), 350)) -- Returns 8050
Section 41.26: CharIndex
Returns the start index of a the first occurrence of string expression inside another string expression.
Parameters list:
String to find (up to 8000 chars) 1. String to search (any valid character data type and length, including binary) 2. (Optional) index to start. A number of type int or big int. If omitted or less then 1, the search starts at the 3.
beginning of the string.
If the string to search is varchar(max), nvarchar(max) or varbinary(max), the CHARINDEX function will return a bigint value. Otherwise, it will return an int.
SELECT CHARINDEX('is', 'this is my string') -- returns 3 SELECT CHARINDEX('is', 'this is my string', 4) -- returns 6 SELECT CHARINDEX(' is', 'this is my string') -- returns 5
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Chapter 42: Logical Functions
Section 42.1: CHOOSE
Version ≥ SQL Server 2012
Returns the item at the specified index from a list of values. If index exceeds the bounds of values then NULL is returned.
Parameters:
index: integer, index to item in values. 1-based. 1. values: any type, comma separated list 2.
SELECT CHOOSE (1, 'apples', 'pears', 'oranges', 'bananas') AS chosen_result
chosen_result ------------- apples
Section 42.2: IIF
Version ≥ SQL Server 2012
Returns one of two values, depending on whether a given Boolean expression evaluates to true or false.
Parameters:
boolean_expression evaluated to dtermine what value to return 1. true_value returned if boolean_expression evaluates to true 2. false_value returned if boolean_expression evaluates to false 3.
SELECT IIF (42 > 23, 'I knew that!', 'That is not true.') AS iif_result
iif_result ------------ I knew that!
Version < SQL Server 2012
IIF may be replaced by a CASE statement. The above example my be written as
SELECT CASE WHEN 42 > 23 THEN 'I knew that!' ELSE 'That is not true.' END AS iif_result
iif_result ------------ I knew that!
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Chapter 43: Aggregate Functions
Aggregate functions in SQL Server run calculations on sets of values, returning a single value.
Section 43.1: SUM()
Returns sum of numeric values in a given column.
We have table as shown in figure that will be used to perform different aggregate functions. The table name is Marksheet.
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Select SUM(MarksObtained) From Marksheet
The sum function doesn't consider rows with NULL value in the field used as parameter
In the above example if we have another row like this:
106 Italian NULL
This row will not be consider in sum calculation
Section 43.2: AVG()
Returns average of numeric values in a given column.
We have table as shown in figure that will be used to perform different aggregate functions. The table name is Marksheet.
Select AVG(MarksObtained) From Marksheet
The average function doesn't consider rows with NULL value in the field used as parameter
In the above example if we have another row like this:
106 Italian NULL
This row will not be consider in average calculation
Section 43.3: MAX()
Returns the largest value in a given column.
We have table as shown in figure that will be used to perform different aggregate functions. The table name is Marksheet.
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Select MAX(MarksObtained) From Marksheet
Section 43.4: MIN()
Returns the smallest value in a given column.
We have table as shown in figure that will be used to perform different aggregate functions. The table name is Marksheet.
Select MIN(MarksObtained) From Marksheet
Section 43.5: COUNT()
Returns the total number of values in a given column.
We have table as shown in figure that will be used to perform different aggregate functions. The table name is Marksheet.
Select COUNT(MarksObtained) From Marksheet
The count function doesn't consider rows with NULL value in the field used as parameter. Usually the count parameter is * (all fields) so only if all fields of row are NULLs this row will not be considered
In the above example if we have another row like this:
106 Italian NULL
This row will not be consider in count calculation
NOTE
The function COUNT(*) returns the number of rows in a table. This value can also be obtained by using a constant non-null expression that contains no column references, such as COUNT(1).
Example
Select COUNT(1) From Marksheet
Section 43.6: COUNT(Column_Name) with GROUP BY Column_Name
Most of the time we like to get the total number of occurrence of a column value in a table for example:
TABLE NAME : REPORTS
ReportNameReportPrice Test 10.00 $
Test 10.00 $
Test 10.00 $ Test 2 11.00 $
Test 10.00 $
Test 3 14.00 $
Test 3 14.00 $
Test 4 100.00 $
SELECT
ReportName AS REPORT NAME, COUNT(ReportName) AS COUNT FROM
REPORTS GROUP BY
ReportName
REPORT NAME COUNT Test 4
Test 2 1
Test 3 2 Test 4 1
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Chapter 44: String Aggregate functions in SQL Server
Section 44.1: Using STUFF for string aggregation
We have a Student table with SubjectId. Here the requirement is to concatenate based on subjectId.
All SQL Server versions
create table #yourstudent (subjectid int, studentname varchar(10))
insert into #yourstudent (subjectid, studentname) values
( 1 ,'Mary' ) ,( 1 ,'John' ) ,( 1 ,'Sam' ) ,( 2 ,'Alaina') ,( 2 ,'Edward')
select subjectid, stuff(( select concat( ',', studentname) from #yourstudent y where y.subjectid = u.subjectid for xml path('')),1,1, '')
from #yourstudent u group by subjectid
Section 44.2: String_Agg for String Aggregation
In case of SQL Server 2017 or vnext we can use in-built STRING_AGG for this aggregation. For same student table,
create table #yourstudent (subjectid int, studentname varchar(10))
insert into #yourstudent (subjectid, studentname) values
( 1 ,'Mary' ) ,( 1 ,'John' ) ,( 1 ,'Sam' ) ,( 2 ,'Alaina') ,( 2 ,'Edward')
select subjectid, string_agg(studentname, ',') from #yourstudent
group by subjectid
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Chapter 45: Ranking Functions
Arguments Details
<partition_by_clause>
Divides the result set produced by the FROM clause into partitions to which the DENSE_RANK function is applied. For the PARTITION BY syntax, see OVER Clause (Transact-SQL).
<order_by_clause>
Determines the order in which the DENSE_RANK function is applied to the rows in a partition.
OVER ( [ partition_by_clause ] order_by_clause)
partition_by_clause divides the result set produced by the FROM clause into partitions to which the function is applied. If not specified, the function treats all rows of the query result set as a single group. order_by_clause determines the order of the data before the function is applied. The order_by_clause is required. The <rows or range clause> of the OVER clause cannot be specified for the RANK function. For more information, see OVER Clause (Transact-SQL).
Section 45.1: DENSE_RANK ()
Same as that of RANK(). It returns rank without any gaps:
Select Studentid, Name,Subject,Marks, DENSE_RANK() over(partition by name order by Marks desc)Rank From Exam order by name
Studentid Name Subject Marks Rank 101 Ivan Science 80 1 101 Ivan Maths 70 2 101 Ivan Social 60 3 102 Ryan Social 70 1 102 Ryan Maths 60 2 102 Ryan Science 50 3 103 Tanvi Maths 90 1 103 Tanvi Science 90 1 103 Tanvi Social 80 2
Section 45.2: RANK()
A RANK() Returns the rank of each row in the result set of partitioned column.
Eg :
Select Studentid,Name,Subject,Marks, RANK() over(partition by name order by Marks desc)Rank From Exam order by name,subject
Studentid Name Subject Marks Rank
101 Ivan Maths 70 2 101 Ivan Science 80 1 101 Ivan Social 60 3 102 Ryan Maths 60 2 102 Ryan Science 50 3 102 Ryan Social 70 1 103 Tanvi Maths 90 1 103 Tanvi Science 90 1 103 Tanvi Social 80 3
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Chapter 46: Window functions
Section 46.1: Centered Moving Average
Calculate a 6-month (126-business-day) centered moving average of a price:
SELECT TradeDate, AVG(Px) OVER (ORDER BY TradeDate ROWS BETWEEN 63 PRECEDING AND 63 FOLLOWING) AS PxMovingAverage FROM HistoricalPrices
Note that, because it will take up to 63 rows before and after each returned row, at the beginning and end of the TradeDate range it will not be centered: When it reaches the largest TradeDate it will only be able to find 63 preceding values to include in the average.
Section 46.2: Find the single most recent item in a list of timestamped events
In tables recording events there is often a datetime field recording the time an event happened. Finding the single most recent event can be difficult because it's always possible that two events were recorded with exactly identical timestamps. You can use row_number() over (order by ...) to make sure all records are uniquely ranked, and select the top one (where my_ranking=1)
select * from (
select *, row_number() over (order by crdate desc) as my_ranking from sys.sysobjects ) g where my_ranking=1
This same technique can be used to return a single row from any dataset with potentially duplicate values.
Section 46.3: Moving Average of last 30 Items
Moving Average of last 30 Items sold
SELECT
value_column1, ( SELECT
AVG(value_column1) AS moving_average FROM Table1 T2 WHERE ( SELECT
COUNT(*) FROM Table1 T3 WHERE date_column1 BETWEEN T2.date_column1 AND T1.date_column1 ) BETWEEN 1 AND 30 ) as MovingAvg FROM Table1 T1
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Chapter 47: PIVOT / UNPIVOT
Section 47.1: Dynamic PIVOT
One problem with the PIVOT query is that you have to specify all values inside the IN selection if you want to see them as columns. A quick way to circumvent this problem is to create a dynamic IN selection making your PIVOT dynamic.
For demonstration we will use a table Books in a Bookstore’s database. We assume that the table is quite de- normalised and has following columns
Table: Books ----------------------------- BookId (Primary Key Column) Name Language NumberOfPages EditionNumber YearOfPrint YearBoughtIntoStore ISBN AuthorName Price NumberOfUnitsSold
Creation script for the table will be like:
CREATE TABLE [dbo].[BookList]( [BookId] [int] NOT NULL, [Name] [nvarchar](100) NULL, [Language] [nvarchar](100) NULL, [NumberOfPages] [int] NULL, [EditionNumber] [nvarchar](10) NULL, [YearOfPrint] [int] NULL, [YearBoughtIntoStore] [int] NULL, [NumberOfBooks] [int] NULL, [ISBN] [nvarchar](30) NULL,
[AuthorName] [nvarchar](200) NULL, [Price] [money] NULL, [NumberOfUnitsSold] [int] NULL, CONSTRAINT [PK_BookList] PRIMARY KEY CLUSTERED (
[BookId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY]
GO
Now if we need to query on the database and figure out number of books in English, Russian, German, Hindi, Latin languages bought into the bookstore every year and present our output in a small report format, we can use PIVOT query like this
SELECT * FROM
(
SELECT YearBoughtIntoStore AS [Year Bought],[Language], NumberOfBooks FROM BookList
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) sourceData PIVOT
( SUM(NumberOfBooks) FOR [Language] IN (English, Russian, German, Hindi, Latin) ) pivotrReport
Special case is when we do not have a full list of the languages, so we'll use dynamic SQL like below
DECLARE @query VARCHAR(4000) DECLARE @languages VARCHAR(2000) SELECT @languages =
STUFF((SELECT DISTINCT '],['+LTRIM([Language])FROM [dbo].[BookList] ORDER BY '],['+LTRIM([Language]) FOR XML PATH('') ),1,2,'') + ']' SET @query= 'SELECT * FROM
(SELECT YearBoughtIntoStore AS [Year Bought],[Language],NumberOfBooks
FROM BookList) sourceData PIVOT(SUM(NumberOfBooks)FOR [Language] IN ('+ @languages +')) pivotrReport' EXECUTE(@query)
Section 47.2: Simple PIVOT & UNPIVOT (T-SQL)
Below is a simple example which shows average item's price of each item per weekday.
First, suppose we have a table which keeps daily records of all items' prices.
CREATE TABLE tbl_stock(item NVARCHAR(10), weekday NVARCHAR(10), price INT);
INSERT INTO tbl_stock VALUES ('Item1', 'Mon', 110), ('Item2', 'Mon', 230), ('Item3', 'Mon', 150), ('Item1', 'Tue', 115), ('Item2', 'Tue', 231), ('Item3', 'Tue', 162), ('Item1', 'Wed', 110), ('Item2', 'Wed', 240), ('Item3', 'Wed', 162), ('Item1', 'Thu', 109), ('Item2', 'Thu', 228), ('Item3', 'Thu', 145), ('Item1', 'Fri', 120), ('Item2', 'Fri', 210), ('Item3', 'Fri', 125), ('Item1', 'Mon', 122), ('Item2', 'Mon', 225), ('Item3', 'Mon', 140), ('Item1', 'Tue', 110), ('Item2', 'Tue', 235), ('Item3', 'Tue', 154), ('Item1', 'Wed', 125), ('Item2', 'Wed', 220), ('Item3', 'Wed', 142);
The table should look like below:
+========+=========+=======+ | item | weekday | price | +========+=========+=======+ | Item1 | Mon | 110 | +--------+---------+-------+ | Item2 | Mon | 230 | +--------+---------+-------+ | Item3 | Mon | 150 | +--------+---------+-------+ | Item1 | Tue | 115 | +--------+---------+-------+ | Item2 | Tue | 231 | +--------+---------+-------+ | Item3 | Tue | 162 | +--------+---------+-------+ | . . . | +--------+---------+-------+ | Item2 | Wed | 220 | +--------+---------+-------+
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| Item3 | Wed | 142 | +--------+---------+-------+
In order to perform aggregation which is to find the average price per item for each week day, we are going to use the relational operator PIVOT to rotate the column weekday of table-valued expression into aggregated row values as below:
SELECT * FROM tbl_stock PIVOT (
AVG(price) FOR weekday IN ([Mon], [Tue], [Wed], [Thu], [Fri]) ) pvt;
Result:
+--------+------+------+------+------+------+ | item | Mon | Tue | Wed | Thu | Fri | +--------+------+------+------+------+------+ | Item1 | 116 | 112 | 117 | 109 | 120 | | Item2 | 227 | 233 | 230 | 228 | 210 | | Item3 | 145 | 158 | 152 | 145 | 125 | +--------+------+------+------+------+------+
Lastly, in order to perform the reverse operation of PIVOT, we can use the relational operator UNPIVOT to rotate columns into rows as below:
SELECT * FROM tbl_stock PIVOT (
AVG(price) FOR weekday IN ([Mon], [Tue], [Wed], [Thu], [Fri]) ) pvt UNPIVOT (
price FOR weekday IN ([Mon], [Tue], [Wed], [Thu], [Fri]) ) unpvt;
Result:
+=======+========+=========+ | item | price | weekday | +=======+========+=========+ | Item1 | 116 | Mon | +-------+--------+---------+ | Item1 | 112 | Tue | +-------+--------+---------+ | Item1 | 117 | Wed | +-------+--------+---------+ | Item1 | 109 | Thu | +-------+--------+---------+ | Item1 | 120 | Fri | +-------+--------+---------+ | Item2 | 227 | Mon | +-------+--------+---------+ | Item2 | 233 | Tue | +-------+--------+---------+ | Item2 | 230 | Wed | +-------+--------+---------+ | Item2 | 228 | Thu | +-------+--------+---------+ | Item2 | 210 | Fri |
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+-------+--------+---------+ | Item3 | 145 | Mon | +-------+--------+---------+ | Item3 | 158 | Tue | +-------+--------+---------+ | Item3 | 152 | Wed | +-------+--------+---------+ | Item3 | 145 | Thu | +-------+--------+---------+ | Item3 | 125 | Fri | +-------+--------+---------+
Section 47.3: Simple Pivot - Static Columns
Using Item Sales Table from Example Database, let us calculate and show the total Quantity we sold of each Product.
This can be easily done with a group by, but lets assume we to 'rotate' our result table in a way that for each Product Id we have a column.
SELECT [100], [145]
FROM (SELECT ItemId , Quantity
FROM #ItemSalesTable ) AS pivotIntermediate PIVOT ( SUM(Quantity)
FOR ItemId IN ([100], [145]) ) AS pivotTable
Since our 'new' columns are numbers (in the source table), we need to square brackets []
This will give us an output like
100 145 45 18
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Chapter 48: Dynamic SQL Pivot
This topic covers how to do a dynamic pivot in SQL Server.
Section 48.1: Basic Dynamic SQL Pivot
if object_id('tempdb.dbo.#temp') is not null drop table #temp create table #temp (
dateValue datetime, category varchar(3), amount decimal(36,2) )
insert into #temp values ('1/1/2012', 'ABC', 1000.00) insert into #temp values ('2/1/2012', 'DEF', 500.00) insert into #temp values ('2/1/2012', 'GHI', 800.00) insert into #temp values ('2/10/2012', 'DEF', 700.00) insert into #temp values ('3/1/2012', 'ABC', 1100.00)
DECLARE
@cols AS NVARCHAR(MAX), @query AS NVARCHAR(MAX);
SET @cols = STUFF((SELECT distinct ',' + QUOTENAME(c.category)
FROM #temp c FOR XML PATH(''), TYPE ).value('.', 'NVARCHAR(MAX)') ,1,1,'')
set @query = '
SELECT
dateValue, ' + @cols + ' from (
select
dateValue, amount, category from #temp ) x
pivot (
sum(amount) for category in (' + @cols + ') ) p '
exec sp_executeSql @query
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Chapter 49: Partitioning
Section 49.1: Retrieve Partition Boundary Values
SELECT ps.name AS PartitionScheme
, fg.name AS [FileGroup] , prv.* , LAG(prv.Value) OVER (PARTITION BY ps.name ORDER BY ps.name, boundary_id) AS PreviousBoundaryValue
FROM sys.partition_schemes ps INNER JOIN sys.destination_data_spaces dds
ON dds.partition_scheme_id = ps.data_space_id INNER JOIN sys.filegroups fg
ON dds.data_space_id = fg.data_space_id INNER JOIN sys.partition_functions f
ON f.function_id = ps.function_id INNER JOIN sys.partition_range_values prv
ON f.function_id = prv.function_id AND dds.destination_id = prv.boundary_id
Section 49.2: Switching Partitions
According to this [TechNet Microsoft page][1],
Partitioning data enables you to manage and access subsets of your data quickly and efficiently while maintaining the integrity of the entire data collection.
When you call the following query the data is not physically moved; only the metadata about the location of the data changes.
ALTER TABLE [SourceTable] SWITCH TO [TargetTable]
The tables must have the same columns with the same data types and NULL settings, they need to be in the same file group and the new target table must be empty. See the page link above for more info on switching partitions.
[1]: https://technet.microsoft.com/en-us/library/ms191160(v=sql.105).aspx The column IDENTITY property may differ.
Section 49.3: Retrieve partition table,column, scheme, function, total and min-max boundry values using single query
SELECT DISTINCT
object_name(i.object_id) AS [Object Name], c.name AS [Partition Column], s.name AS [Partition Scheme], pf.name AS [Partition Function], prv.tot AS [Partition Count], prv.miVal AS [Min Boundry Value], prv.maVal AS [Max Boundry Value] FROM sys.objects o INNER JOIN sys.indexes i ON i.object_id = o.object_id INNER JOIN sys.columns c ON c.object_id = o.object_id
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INNER JOIN sys.index_columns ic ON ic.object_id = o.object_id
AND ic.column_id = c.column_id AND ic.partition_ordinal = 1 INNER JOIN sys.partition_schemes s ON i.data_space_id = s.data_space_id INNER JOIN sys.partition_functions pf ON pf.function_id = s.function_id OUTER APPLY(SELECT
COUNT(*) tot, MIN(value) miVal, MAX(value) maVal FROM sys.partition_range_values prv WHERE prv.function_id = pf.function_id) prv --WHERE object_name(i.object_id) = 'table_name' ORDER BY OBJECT_NAME(i.object_id)
Just un-comment where clause and replace table_name with actual table name to view the detail of desired object.
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Chapter 50: Stored Procedures
In SQL Server, a procedure is a stored program that you can pass parameters into. It does not return a value like a function does. However, it can return a success/failure status to the procedure that called it.
Section 50.1: Creating and executing a basic stored procedure
Using the Authors table in the Library Database
CREATE PROCEDURE GetName (
@input_id INT = NULL, --Input parameter, id of the person, NULL default @name VARCHAR(128) = NULL --Input parameter, name of the person, NULL default ) AS BEGIN
SELECT Name + ' is from ' + Country FROM Authors WHERE Id = @input_id OR Name = @name END GO
You can execute a procedure with a few different syntaxes. First, you can use EXECUTE or EXEC
EXECUTE GetName @id = 1 EXEC Getname @name = 'Ernest Hemingway'
Additionally, you can omit the EXEC command. Also, you don't have to specify what parameter you are passing in, as you pass in all parameters.
GetName NULL, 'Ernest Hemingway'
When you want to specify the input parameters in a different order than how they are declared in the procedure you can specify the parameter name and assign values. For example
CREATE PROCEDURE dbo.sProcTemp (
@Param1 INT, @Param2 INT ) AS BEGIN
SELECT
Param1 = @Param1, Param2 = @Param2
END
the normal order to execute this procedure is to specify the value for @Param1 first and then @Param2 second. So it will look something like this
EXEC dbo.sProcTemp @Param1 = 0,@Param2=1
But it's also possible that you can use the following
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EXEC dbo.sProcTemp @Param2 = 0,@Param1=1
in this, you are specifying the value for @param2 first and @Param1 second. Which means you do not have to keep the same order as it is declared in the procedure but you can have any order as you wish. but you will need to specify to which parameter you are setting the value
Access stored procedure from any database
And also you can create a procedure with a prefix sp_ these procuedres, like all system stored procedures, can be executed without specifying the database because of the default behavior of SQL Server. When you execute a stored procedure that starts with "sp_", SQL Server looks for the procedure in the master database first. If the procedure is not found in master, it looks in the active database. If you have a stored procedure that you want to access from all your databases, create it in master and use a name that includes the "sp_" prefix.
Use Master
CREATE PROCEDURE sp_GetName (
@input_id INT = NULL, --Input parameter, id of the person, NULL default @name VARCHAR(128) = NULL --Input parameter, name of the person, NULL default ) AS BEGIN
SELECT Name + ' is from ' + Country FROM Authors WHERE Id = @input_id OR Name = @name END GO
Section 50.2: Stored Procedure with If...Else and Insert Into operation
Create example table Employee:
CREATE TABLE Employee (
Id INT, EmpName VARCHAR(25), EmpGender VARCHAR(6), EmpDeptId INT )
Creates stored procedure that checks whether the values passed in stored procedure are not null or non empty and perform insert operation in Employee table.
CREATE PROCEDURE spSetEmployeeDetails (
@ID int, @Name VARCHAR(25), @Gender VARCHAR(6), @DeptId INT ) AS BEGIN
IF (
(@ID IS NOT NULL AND LEN(@ID) !=0) AND (@Name IS NOT NULL AND LEN(@Name) !=0)
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AND (@Gender IS NOT NULL AND LEN(@Gender) !=0) AND (@DeptId IS NOT NULL AND LEN(@DeptId) !=0) ) BEGIN
INSERT INTO Employee (
Id, EmpName, EmpGender, EmpDeptId ) VALUES (
@ID, @Name, @Gender, @DeptId ) END ELSE
PRINT 'Incorrect Parameters' END GO
Execute the stored procedure
DECLARE @ID INT,
@Name VARCHAR(25), @Gender VARCHAR(6), @DeptId INT
EXECUTE spSetEmployeeDetails
@ID = 1, @Name = 'Subin Nepal', @Gender = 'Male', @DeptId = 182666
Section 50.3: Dynamic SQL in stored procedure
Dynamic SQL enables us to generate and run SQL statements at run time. Dynamic SQL is needed when our SQL statements contains identifier that may change at different compile times.
Simple Example of dynamic SQL:
CREATE PROC sp_dynamicSQL @table_name NVARCHAR(20), @col_name NVARCHAR(20), @col_value NVARCHAR(20) AS BEGIN DECLARE @Query NVARCHAR(max) SET @Query = 'SELECT * FROM ' + @table_name SET @Query = @Query + ' WHERE ' + @col_name + ' = ' + ''''+@col_value+'''' EXEC (@Query) END
In the above sql query, we can see that we can use above query by defining values in @table_name, @col_name, and @col_value at run time. The query is generated at runtime and executed. This is technique in which we can create whole scripts as string in a variable and execute it. We can create more complex queries using dynamic SQL
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and concatenation concept. This concept is very powerful when you want to create a script that can be used under several conditions.
Executing stored procedure
DECLARE @table_name NVARCHAR(20) = 'ITCompanyInNepal',
@col_name NVARCHAR(20) = 'Headquarter', @col_value NVARCHAR(20) = 'USA'
EXEC sp_dynamicSQL @table_name,
@col_name, @col_value
Table I have used
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Output
Section 50.4: STORED PROCEDURE with OUT parameters
Stored procedures can return values using the OUTPUT keyword in its parameter list.
Creating a stored procedure with a single out parameter
CREATE PROCEDURE SprocWithOutParams (
@InParam VARCHAR(30), @OutParam VARCHAR(30) OUTPUT ) AS BEGIN
SELECT @OutParam = @InParam + ' must come out' RETURN END GO
Executing the stored procedure
DECLARE @OutParam VARCHAR(30) EXECUTE SprocWithOutParams 'what goes in', @OutParam OUTPUT PRINT @OutParam
Creating a stored procedure with multiple out parameters
CREATE PROCEDURE SprocWithOutParams2 (
@InParam VARCHAR(30), @OutParam VARCHAR(30) OUTPUT, @OutParam2 VARCHAR(30) OUTPUT ) AS BEGIN
SELECT @OutParam = @InParam +' must come out' SELECT @OutParam2 = @InParam +' must come out' RETURN END GO
Executing the stored procedure
DECLARE @OutParam VARCHAR(30) DECLARE @OutParam2 VARCHAR(30) EXECUTE SprocWithOutParams2 'what goes in', @OutParam OUTPUT, @OutParam2 OUTPUT PRINT @OutParam PRINT @OutParam2
Section 50.5: Simple Looping
First lets get some data into a temp table named #systables and ad a incrementing row number so we can query one record at a time
select
o.name, row_number() over (order by o.name) as rn into
#systables from
sys.objects as o where
o.type = 'S'
Next we declare some variables to control the looping and store the table name in this example
declare
@rn int = 1, @maxRn int = (
select
max(rn) from
#systables as s ) declare @tablename sys name
Now we can loop using a simple while. We increment @rn in the select statement but this could also have been a separate statement for ex set @rn = @rn + 1 it will depend on your requirements. We also use the value of @rn before it's incremented to select a single record from #systables. Lastly we print the table name.
while @rn <= @maxRn
begin
select
@tablename = name, @rn = @rn + 1 from
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#systables as s where
s.rn = @rn
print @tablename end
Section 50.6: Simple Looping
CREATE PROCEDURE SprocWithSimpleLoop (
@SayThis VARCHAR(30), @ThisManyTimes INT ) AS BEGIN
WHILE @ThisManyTimes > 0 BEGIN
PRINT @SayThis; SET @ThisManyTimes = @ThisManyTimes - 1; END
RETURN; END GO
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Chapter 51: Retrieve information about the database
Section 51.1: Retrieve a List of all Stored Procedures
The following queries will return a list of all Stored Procedures in the database, with basic information about each Stored Procedure:
Version ≥ SQL Server 2005
SELECT * FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_TYPE = 'PROCEDURE'
The ROUTINE_NAME, ROUTINE_SCHEMA and ROUTINE_DEFINITION columns are generally the most useful.
Version ≥ SQL Server 2005
SELECT * FROM sys.objects WHERE type = 'P'
Version ≥ SQL Server 2005
SELECT * FROM sys.procedures
Note that this version has an advantage over selecting from sys.objects since it includes the additional columns is_auto_executed, is_execution_replicated, is_repl_serializable, and skips_repl_constraints.
Version < SQL Server 2005
SELECT * FROM sysobjects WHERE type = 'P'
Note that the output contains many columns that will never relate to a stored procedure.
The next set of queries will return all Stored Procedures in the database that include the string 'SearchTerm':
Version < SQL Server 2005
SELECT o.name FROM syscomments c INNER JOIN sysobjects o
ON c.id=o.id WHERE o.xtype = 'P'
AND c.TEXT LIKE '%SearchTerm%'
Version ≥ SQL Server 2005
SELECT p.name FROM sys.sql_modules AS m INNER JOIN sys.procedures AS p
ON m.object_id = p.object_id WHERE definition LIKE '%SearchTerm%'
Section 51.2: Get the list of all databases on a server
Method 1: Below query will be applicable for SQL Server 2000+ version (Contains 12 columns)
SELECT * FROM dbo.sysdatabases
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Method 2: Below query extract information about databases with more information (eg: State, Isolation, recovery model etc.)
Note: This is a catalog view and will be available SQL SERVER 2005+ versions
SELECT * FROM sys.databases
Method 3: To see just database names you can use undocumented sp_MSForEachDB
EXEC sp_MSForEachDB 'SELECT ''?'' AS DatabaseName'
Method 4: Below SP will help you to provide database size along with databases name , owner, status etc. on the server
EXEC sp_helpdb
Method 5 Similarly, below stored procedure will give database name, database size and Remarks
EXEC sp_databases
Section 51.3: Count the Number of Tables in a Database
This query will return the number of tables in the specified database.
USE YourDatabaseName SELECT COUNT(*) from INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE'
Following is another way this can be done for all user tables with SQL Server 2008+. The reference is here.
SELECT COUNT(*) FROM sys.tables
Section 51.4: Database Files
Display all data files for all databases with size and growth info
SELECT d.name AS 'Database',
d.database_id, SF.fileid, SF.name AS 'LogicalFileName', CASE SF.status & 0x100000
WHEN 1048576 THEN 'Percentage' WHEN 0 THEN 'MB' END AS 'FileGrowthOption', Growth AS GrowthUnit, ROUND(((CAST(Size AS FLOAT)*8)/1024)/1024,2) [SizeGB], -- Convert 8k pages to GB Maxsize, filename AS PhysicalFileName
FROM Master.SYS.SYSALTFILES SF Join Master.SYS.Databases d on sf.fileid = d.database_id
Order by d.name
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Section 51.5: See if Enterprise-specific features are being used
It is sometimes useful to verify that your work on Developer edition hasn't introduced a dependency on any features restricted to Enterprise edition.
You can do this using the sys.dm_db_persisted_sku_features system view, like so:
SELECT * FROM sys.dm_db_persisted_sku_features
Against the database itself.
This will list the features being used, if any.
Section 51.6: Determine a Windows Login's Permission Path
This will show the user type and permission path (which windows group the user is getting its permissions from).
xp_logininfo 'DOMAIN\user'
Section 51.7: Search and Return All Tables and Columns Containing a Specified Column Value
This script, from here and here, will return all Tables and Columns where a specified value exists. This is powerful in finding out where a certain value is in a database. It can be taxing, so it is suggested that it be executed in a backup / test enviroment first.
DECLARE @SearchStr nvarchar(100) SET @SearchStr = '## YOUR STRING HERE ##'
-- Copyright © 2002 Narayana Vyas Kondreddi. All rights reserved. -- Purpose: To search all columns of all tables for a given search string -- Written by: Narayana Vyas Kondreddi -- Site: http://vyaskn.tripod.com -- Updated and tested by Tim Gaunt -- http://www.thesitedoctor.co.uk -- http://blogs.thesitedoctor.co.uk/tim/2010/02/19/Search+Every+Table+And+Field+In+A+SQL+Server+Databa se+Updated.aspx
-- Tested on: SQL Server 7.0, SQL Server 2000, SQL Server 2005 and SQL Server 2010 -- Date modified: 03rd March 2011 19:00 GMT CREATE TABLE #Results (ColumnName nvarchar(370), ColumnValue nvarchar(3630))
SET NOCOUNT ON
DECLARE @TableName nvarchar(256), @ColumnName nvarchar(128), @SearchStr2 nvarchar(110) SET @TableName = '' SET @SearchStr2 = QUOTENAME('%' + @SearchStr + '%','''')
WHILE @TableName IS NOT NULL
BEGIN
SET @ColumnName = '' SET @TableName = (
SELECT MIN(QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME)) FROM INFORMATION_SCHEMA.TABLES
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WHERE TABLE_TYPE = 'BASE TABLE'
AND QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME) > @TableName AND OBJECTPROPERTY(
OBJECT_ID(
QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME)
), 'IsMSShipped'
) = 0 )
WHILE (@TableName IS NOT NULL) AND (@ColumnName IS NOT NULL)
BEGIN
SET @ColumnName = (
SELECT MIN(QUOTENAME(COLUMN_NAME)) FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = PARSENAME(@TableName, 2)
AND TABLE_NAME = PARSENAME(@TableName, 1) AND DATA_TYPE IN ('char', 'varchar', 'nchar', 'nvarchar', 'int', 'decimal') AND QUOTENAME(COLUMN_NAME) > @ColumnName )
IF @ColumnName IS NOT NULL
BEGIN
INSERT INTO #Results EXEC (
'SELECT ''' + @TableName + '.' + @ColumnName + ''', LEFT(' + @ColumnName + ', 3630) FROM ' + @TableName + ' (NOLOCK) ' +
' WHERE ' + @ColumnName + ' LIKE ' + @SearchStr2 ) END END END
SELECT ColumnName, ColumnValue FROM #Results
DROP TABLE #Results -- See more at: http://thesitedoctor.co.uk/blog/search-every-table-and-field-in-a-sql-server-database-updated#sthas h.bBEqfJVZ.dpuf
Section 51.8: Get all schemas, tables, columns and indexes
SELECT
s.name AS [schema], t.object_id AS [table_object_id], t.name AS [table_name], c.column_id, c.name AS [column_name], i.name AS [index_name], i.type_desc AS [index_type] FROM sys.schemas AS s INNER JOIN sys.tables AS t
ON s.schema_id = t.schema_id INNER JOIN sys.columns AS c
ON t.object_id = c.object_id LEFT JOIN sys.index_columns AS ic
ON c.object_id = ic.object_id and c.column_id = ic.column_id LEFT JOIN sys.indexes AS i
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ON ic.object_id = i.object_id and ic.index_id = i.index_id ORDER BY [schema], [table_name], c.column_id;
Section 51.9: Return a list of SQL Agent jobs, with schedule information
USE msdb Go
SELECT dbo.sysjobs.Name AS 'Job Name',
'Job Enabled' = CASE dbo.sysjobs.Enabled
WHEN 1 THEN 'Yes' WHEN 0 THEN 'No' END, 'Frequency' = CASE dbo.sysschedules.freq_type
WHEN 1 THEN 'Once' WHEN 4 THEN 'Daily' WHEN 8 THEN 'Weekly' WHEN 16 THEN 'Monthly' WHEN 32 THEN 'Monthly relative' WHEN 64 THEN 'When SQLServer Agent starts' END, 'Start Date' = CASE active_start_date
WHEN 0 THEN null ELSE substring(convert(varchar(15),active_start_date),1,4) + '/' + substring(convert(varchar(15),active_start_date),5,2) + '/' + substring(convert(varchar(15),active_start_date),7,2) END, 'Start Time' = CASE len(active_start_time)
WHEN 1 THEN cast('00:00:0' + right(active_start_time,2) as char(8)) WHEN 2 THEN cast('00:00:' + right(active_start_time,2) as char(8)) WHEN 3 THEN cast('00:0'
+ Left(right(active_start_time,3),1) +':' + right(active_start_time,2) as char (8)) WHEN 4 THEN cast('00:'
+ Left(right(active_start_time,4),2) +':' + right(active_start_time,2) as char (8)) WHEN 5 THEN cast('0'
+ Left(right(active_start_time,5),1) +':' + Left(right(active_start_time,4),2) +':' + right(active_start_time,2) as char (8)) WHEN 6 THEN cast(Left(right(active_start_time,6),2)
+':' + Left(right(active_start_time,4),2) +':' + right(active_start_time,2) as char (8)) END,
CASE len(run_duration)
WHEN 1 THEN cast('00:00:0'
+ cast(run_duration as char) as char (8)) WHEN 2 THEN cast('00:00:'
+ cast(run_duration as char) as char (8)) WHEN 3 THEN cast('00:0'
+ Left(right(run_duration,3),1) +':' + right(run_duration,2) as char (8)) WHEN 4 THEN cast('00:'
+ Left(right(run_duration,4),2) +':' + right(run_duration,2) as char (8)) WHEN 5 THEN cast('0'
+ Left(right(run_duration,5),1)
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+':' + Left(right(run_duration,4),2) +':' + right(run_duration,2) as char (8)) WHEN 6 THEN cast(Left(right(run_duration,6),2)
+':' + Left(right(run_duration,4),2) +':' + right(run_duration,2) as char (8)) END as 'Max Duration', CASE(dbo.sysschedules.freq_subday_interval)
WHEN 0 THEN 'Once' ELSE cast('Every '
+ right(dbo.sysschedules.freq_subday_interval,2) + ' ' + CASE(dbo.sysschedules.freq_subday_type)
WHEN 1 THEN 'Once' WHEN 4 THEN 'Minutes' WHEN 8 THEN 'Hours' END as char(16)) END as 'Subday Frequency' FROM dbo.sysjobs LEFT OUTER JOIN dbo.sysjobschedules ON dbo.sysjobs.job_id = dbo.sysjobschedules.job_id INNER JOIN dbo.sysschedules ON dbo.sysjobschedules.schedule_id = dbo.sysschedules.schedule_id LEFT OUTER JOIN (SELECT job_id, max(run_duration) AS run_duration
FROM dbo.sysjobhistory GROUP BY job_id) Q1 ON dbo.sysjobs.job_id = Q1.job_id WHERE Next_run_time = 0
UNION
SELECT dbo.sysjobs.Name AS 'Job Name',
'Job Enabled' = CASE dbo.sysjobs.Enabled
WHEN 1 THEN 'Yes' WHEN 0 THEN 'No' END, 'Frequency' = CASE dbo.sysschedules.freq_type
WHEN 1 THEN 'Once' WHEN 4 THEN 'Daily' WHEN 8 THEN 'Weekly' WHEN 16 THEN 'Monthly' WHEN 32 THEN 'Monthly relative' WHEN 64 THEN 'When SQLServer Agent starts' END, 'Start Date' = CASE next_run_date
WHEN 0 THEN null ELSE substring(convert(varchar(15),next_run_date),1,4) + '/' + substring(convert(varchar(15),next_run_date),5,2) + '/' + substring(convert(varchar(15),next_run_date),7,2) END, 'Start Time' = CASE len(next_run_time)
WHEN 1 THEN cast('00:00:0' + right(next_run_time,2) as char(8)) WHEN 2 THEN cast('00:00:' + right(next_run_time,2) as char(8)) WHEN 3 THEN cast('00:0'
+ Left(right(next_run_time,3),1) +':' + right(next_run_time,2) as char (8)) WHEN 4 THEN cast('00:'
+ Left(right(next_run_time,4),2) +':' + right(next_run_time,2) as char (8)) WHEN 5 THEN cast('0' + Left(right(next_run_time,5),1)
+':' + Left(right(next_run_time,4),2) +':' + right(next_run_time,2) as char (8)) WHEN 6 THEN cast(Left(right(next_run_time,6),2)
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+':' + Left(right(next_run_time,4),2) +':' + right(next_run_time,2) as char (8)) END,
CASE len(run_duration)
WHEN 1 THEN cast('00:00:0'
+ cast(run_duration as char) as char (8)) WHEN 2 THEN cast('00:00:'
+ cast(run_duration as char) as char (8)) WHEN 3 THEN cast('00:0'
+ Left(right(run_duration,3),1) +':' + right(run_duration,2) as char (8)) WHEN 4 THEN cast('00:'
+ Left(right(run_duration,4),2) +':' + right(run_duration,2) as char (8)) WHEN 5 THEN cast('0'
+ Left(right(run_duration,5),1) +':' + Left(right(run_duration,4),2) +':' + right(run_duration,2) as char (8)) WHEN 6 THEN cast(Left(right(run_duration,6),2)
+':' + Left(right(run_duration,4),2) +':' + right(run_duration,2) as char (8)) END as 'Max Duration', CASE(dbo.sysschedules.freq_subday_interval)
WHEN 0 THEN 'Once' ELSE cast('Every '
+ right(dbo.sysschedules.freq_subday_interval,2) + ' ' + CASE(dbo.sysschedules.freq_subday_type)
WHEN 1 THEN 'Once' WHEN 4 THEN 'Minutes' WHEN 8 THEN 'Hours' END as char(16)) END as 'Subday Frequency' FROM dbo.sysjobs LEFT OUTER JOIN dbo.sysjobschedules ON dbo.sysjobs.job_id = dbo.sysjobschedules.job_id INNER JOIN dbo.sysschedules ON dbo.sysjobschedules.schedule_id = dbo.sysschedules.schedule_id LEFT OUTER JOIN (SELECT job_id, max(run_duration) AS run_duration
FROM dbo.sysjobhistory GROUP BY job_id) Q1 ON dbo.sysjobs.job_id = Q1.job_id WHERE Next_run_time <> 0
ORDER BY [Start Date],[Start Time]
Section 51.10: Retrieve Tables Containing Known Column
This query will return all COLUMNS and their associated TABLES for a given column name. It is designed to show you what tables (unknown) contain a specified column (known)
SELECT
c.name AS ColName, t.name AS TableName FROM
sys.columns c JOIN sys.tables t ON c.object_id = t.object_id WHERE
c.name LIKE '%MyName%'
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Section 51.11: Show Size of All Tables in Current Database
SELECT
s.name + '.' + t.NAME AS TableName, SUM(a.used_pages)*8 AS 'TableSizeKB' --a page in SQL Server is 8kb FROM sys.tables t
JOIN sys.schemas s on t.schema_id = s.schema_id LEFT JOIN sys.indexes i ON t.OBJECT_ID = i.object_id LEFT JOIN sys.partitions p ON i.object_id = p.OBJECT_ID AND i.index_id = p.index_id LEFT JOIN sys.allocation_units a ON p.partition_id = a.container_id GROUP BY
s.name, t.name ORDER BY
--Either sort by name: s.name + '.' + t.NAME --Or sort largest to smallest: --SUM(a.used_pages) desc
Section 51.12: Retrieve Database Options
The following query returns the database options and metadata:
select * from sys.databases WHERE name = 'MyDatabaseName';
Section 51.13: Find every mention of a field in the database
SELECT DISTINCT
o.name AS Object_Name,o.type_desc FROM sys.sql_modules m
INNER JOIN sys.objects o ON m.object_id=o.object_id WHERE m.definition Like '%myField%' ORDER BY 2,1
Will find mentions of myField in SProcs, Views, etc.
Section 51.14: Retrieve information on backup and restore operations
To get the list of all backup operations performed on the current database instance:
SELECT sdb.Name AS DatabaseName,
COALESCE(CONVERT(VARCHAR(50), bus.backup_finish_date, 120),'-') AS LastBackUpDateTime FROM sys.sysdatabases sdb
LEFT OUTER JOIN msdb.dbo.backupset bus ON bus.database_name = sdb.name ORDER BY sdb.name, bus.backup_finish_date DESC
To get the list of all restore operations performed on the current database instance:
SELECT
[d].[name] AS database_name, [r].restore_date AS last_restore_date, [r].[user_name], [bs].[backup_finish_date] AS backup_creation_date, [bmf].[physical_device_name] AS [backup_file_used_for_restore] FROM master.sys.databases [d]
LEFT OUTER JOIN msdb.dbo.[restorehistory] r ON r.[destination_database_name] = d.Name INNER JOIN msdb.dbo.backupset [bs] ON [r].[backup_set_id] = [bs].[backup_set_id]
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INNER JOIN msdb.dbo.backupmediafamily bmf ON [bs].[media_set_id] = [bmf].[media_set_id] ORDER BY [d].[name], [r].restore_date DESC
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Chapter 52: Split String function in SQL Server
Section 52.1: Split string in Sql Server 2008/2012/2014 using XML
Since there is no STRING_SPLIT function we need to use XML hack to split the string into rows:
Example:
SELECT split.a.value('.', 'VARCHAR(100)') AS Value FROM (SELECT Cast ('<M>' + Replace('A|B|C', '|', '</M><M>')+ '</M>' AS XML) AS Data) AS A
CROSS apply data.nodes ('/M') AS Split(a);
Result:
+-----+ |Value| +-----+ |A | +-----+ |B | +-----+ |C | +-----+
Section 52.2: Split a String in Sql Server 2016
In SQL Server 2016 finally they have introduced Split string function : STRING_SPLIT
Parameters: It accepts two parameters
String:
Is an expression of any character type (i.e. nvarchar, varchar, nchar or char).
separator :
Is a single character expression of any character type (e.g. nvarchar(1), varchar(1), nchar(1) or char(1)) that is used as separator for concatenated strings.
Note: You should always check if the expression is a non-empty string.
Example:
Select Value From STRING_SPLIT('a|b|c','|')
In above example
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String : 'a|b|c' separator : '|'
Result :
+-----+ |Value| +-----+ |a | +-----+ |b | +-----+ |c | +-----+
If it's an empty string:
SELECT value FROM STRING_SPLIT('',',')
Result :
+-----+ |Value| +-----+ 1 | | +-----+
You can avoid the above situation by adding a WHERE clause
SELECT value FROM STRING_SPLIT('',',') WHERE LTRIM(RTRIM(value))<>''
Section 52.3: T-SQL Table variable and XML
Declare @userList Table(UserKey VARCHAR(60)) Insert into @userList values ('bill'),('jcom'),('others') --Declared a table variable and insert 3 records
Declare @text XML Select @text = (
select UserKey from @userList for XML Path('user'), root('group') ) --Set the XML value from Table
Select @text
--View the variable value XML: \<group>\<user>\<UserKey>bill\</UserKey>\</user>\<user>\<UserKey>jcom\</UserKey>\</user>\<user>\<Us erKey>others\</UserKey>\</user>\</group>
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Chapter 53: Insert
Section 53.1: Add a row to a table named Invoices
INSERT INTO Invoices [ /* column names may go here */ ] VALUES (123, '1234abc', '2016-08-05 20:18:25.770', 321, 5, '2016-08-04');
Column names are required if the table you are inserting into contains a column with the IDENTITY attribute.
INSERT INTO Invoices ([ID], [Num], [DateTime], [Total], [Term], [DueDate]) VALUES (123, '1234abc', '2016-08-05 20:18:25.770', 321, 5, '2016-08-25');
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Chapter 54: Primary Keys
Section 54.1: Create table w/ identity column as primary key
-- Identity primary key - unique arbitrary increment number create table person ( id int identity(1,1) primary key not null, firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) not null )
Section 54.2: Create table w/ GUID primary key
-- GUID primary key - arbitrary unique value for table create table person ( id uniqueIdentifier default (newId()) primary key, firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) not null )
Section 54.3: Create table w/ natural key
-- natural primary key - using an existing piece of data within the table that uniquely identifies the record
create table person ( firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) primary key not null )
Section 54.4: Create table w/ composite key
-- composite key - using two or more existing columns within a table to create a primary key create table person ( firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) not null, primary key (firstName, lastName, dob) )
Section 54.5: Add primary key to existing table
ALTER TABLE person
ADD CONSTRAINT pk_PersonSSN PRIMARY KEY (ssn)
Note, if the primary key column (in this case ssn) has more than one row with the same candidate key, the above statement will fail, as primary key values must be unique.
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Section 54.6: Delete primary key
ALTER TABLE Person
DROP CONSTRAINT pk_PersonSSN
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Chapter 55: Foreign Keys
Section 55.1: Foreign key relationship/constraint
Foreign keys enables you to define relationship between two tables. One (parent) table need to have primary key that uniquely identifies rows in the table. Other (child) table can have value of the primary key from the parent in one of the columns. FOREIGN KEY REFERENCES constraint ensures that values in child table must exist as a primary key value in the parent table.
In this example we have parent Company table with CompanyId primary key, and child Employee table that has id of the company where this employee works.
create table Company (
CompanyId int primary key, Name nvarchar(200) ) create table Employee ( EmployeeId int, Name nvarchar(200), CompanyId int
foreign key references Company(companyId) )
foreign key references ensures that values inserted in Employee.CompanyId column must also exist in Company.CompanyId column. Also, nobody can delete company in company table if there is ate least one employee with a matching companyId in child table.
FOREIGN KEY relationship ensures that rows in two tables cannot be "unlinked".
Section 55.2: Maintaining relationship between parent/child rows
Let's assume that we have one row in Company table with companyId 1. We can insert row in employee table that has companyId 1:
insert into Employee values (17, 'John', 1)
However, we cannot insert employee that has non-existing CompanyId:
insert into Employee values (17, 'John', 111111)
Msg 547, Level 16, State 0, Line 12 The INSERT statement conflicted with the FOREIGN KEY constraint "FK__Employee__Compan__1EE485AA". The conflict occurred in database "MyDb", table "dbo.Company", column 'CompanyId'. The statement has been terminated.
Also, we cannot delete parent row in company table as long as there is at least one child row in employee table that references it.
delete from company where CompanyId = 1
Msg 547, Level 16, State 0, Line 14 The DELETE statement conflicted with the REFERENCE constraint "FK__Employee__Compan__1EE485AA". The conflict occurred in database "MyDb", table "dbo.Employee", column 'CompanyId'. The statement has been terminated.
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Foreign key relationship ensures that Company and employee rows will not be "unlinked".
Section 55.3: Adding foreign key relationship on existing table
FOREIGN KEY constraint can be added on existing tables that are still not in relationship. Imagine that we have Company and Employee tables where Employee table CompanyId column but don't have foreign key relationship. ALTER TABLE statement enables you to add foreign key constraint on an existing column that references some other table and primary key in that table:
alter table Employee
add foreign key (CompanyId) references Company(CompanyId)
Section 55.4: Add foreign key on existing table
FOREIGN KEY columns with constraint can be added on existing tables that are still not in relationship. Imagine that we have Company and Employee tables where Employee table don't have CompanyId column. ALTER TABLE statement enables you to add new column with foreign key constraint that references some other table and primary key in that table:
alter table Employee
add CompanyId int foreign key references Company(CompanyId)
Section 55.5: Getting information about foreign key constraints
sys.foreignkeys system view returns information about all foreign key relationships in database:
select name,
OBJECT_NAME(referenced_object_id) as [parent table], OBJECT_NAME(parent_object_id) as [child table], delete_referential_action_desc, update_referential_action_desc from sys.foreign_keys
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Chapter 56: Last Inserted Identity
Section 56.1: @@IDENTITY and MAX(ID)
SELECT MAX(Id) FROM Employees -- Display the value of Id in the last row in Employees table. GO INSERT INTO Employees (FName, LName, PhoneNumber) -- Insert a new row VALUES ('John', 'Smith', '25558696525') GO SELECT @@IDENTITY GO SELECT MAX(Id) FROM Employees -- Display the value of Id of the newly inserted row. GO
The last two SELECT statements values are the same.
Section 56.2: SCOPE_IDENTITY()
CREATE TABLE dbo.logging_table(log_id INT IDENTITY(1,1) PRIMARY KEY,
log_message VARCHAR(255))
CREATE TABLE dbo.person(person_id INT IDENTITY(1,1) PRIMARY KEY,
person_name VARCHAR(100) NOT NULL) GO;
CREATE TRIGGER dbo.InsertToADifferentTable ON dbo.person AFTER INSERT AS
INSERT INTO dbo.logging_table(log_message) VALUES('Someone added something to the person table') GO;
INSERT INTO dbo.person(person_name) VALUES('John Doe')
SELECT SCOPE_IDENTITY();
This will return the most recently added identity value produced on the same connection, within the current scope. In this case, 1, for the first row in the dbo.person table.
Section 56.3: @@IDENTITY
CREATE TABLE dbo.logging_table(log_id INT IDENTITY(1,1) PRIMARY KEY,
log_message VARCHAR(255))
CREATE TABLE dbo.person(person_id INT IDENTITY(1,1) PRIMARY KEY,
person_name VARCHAR(100) NOT NULL) GO;
CREATE TRIGGER dbo.InsertToADifferentTable ON dbo.person AFTER INSERT AS
INSERT INTO dbo.logging_table(log_message) VALUES('Someone added something to the person table') GO;
INSERT INTO dbo.person(person_name)
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VALUES('John Doe')
SELECT @@IDENTITY;
This will return the most recently-added identity on the same connection, regardless of scope. In this case, whatever the current value of the identity column on logging_table is, assuming no other activity is occurring on the instance of SQL Server and no other triggers fire from this insert.
Section 56.4: IDENT_CURRENT('tablename')
SELECT IDENT_CURRENT('dbo.person');
This will select the most recently-added identity value on the selected table, regardless of connection or scope.
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Chapter 57: SCOPE_IDENTITY()
Section 57.1: Introduction with Simple Example
SCOPE_IDENTITY() returns the last identity value inserted into an identity column in the same scope. A scope is a module: a stored procedure, trigger, function, or batch. Therefore, two statements are in the same scope if they are in the same stored procedure, function, or batch.
INSERT INTO ([column1],[column2]) VALUES (8,9); GO SELECT SCOPE_IDENTITY() AS [SCOPE_IDENTITY]; GO
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Chapter 58: Sequences
Section 58.1: Create Sequence
CREATE SEQUENCE [dbo].[CustomersSeq] AS INT START WITH 10001 INCREMENT BY 1 MINVALUE -1;
Section 58.2: Use Sequence in Table
CREATE TABLE [dbo].[Customers] (
CustomerID INT DEFAULT (NEXT VALUE FOR [dbo].[CustomersSeq]) NOT NULL, CustomerName VARCHAR(100), );
Section 58.3: Insert Into Table with Sequence
INSERT INTO [dbo].[Customers]
([CustomerName]) VALUES
('Jerry'), ('Gorge')
SELECT * FROM [dbo].[Customers]
Results
CustomerID CustomerName 10001 Jerry
10002 Gorge
Section 58.4: Delete From & Insert New
DELETE FROM [dbo].[Customers] WHERE CustomerName = 'Gorge';
INSERT INTO [dbo].[Customers]
([CustomerName]) VALUES ('George')
SELECT * FROM [dbo].[Customers]
Results
CustomerID CustomerName 10001 Jerry
10003 George
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Chapter 59: Index
Section 59.1: Create Clustered index
With a clustered index the leaf pages contain the actual table rows. Therefore, there can be only one clustered index.
CREATE TABLE Employees (
ID CHAR(900), FirstName NVARCHAR(3000), LastName NVARCHAR(3000), StartYear CHAR(900) ) GO
CREATE CLUSTERED INDEX IX_Clustered ON Employees(ID) GO
Section 59.2: Drop index
DROP INDEX IX_NonClustered ON Employees
Section 59.3: Create Non-Clustered index
Non-clustered indexes have a structure separate from the data rows. A non-clustered index contains the non- clustered index key values and each key value entry has a pointer to the data row that contains the key value. There can be maximum 999 non-clustered index on SQL Server 2008/ 2012.
Link for reference: https://msdn.microsoft.com/en-us/library/ms143432.aspx
CREATE TABLE Employees (
ID CHAR(900), FirstName NVARCHAR(3000), LastName NVARCHAR(3000), StartYear CHAR(900) ) GO
CREATE NONCLUSTERED INDEX IX_NonClustered ON Employees(StartYear) GO
Section 59.4: Show index info
SP_HELPINDEX tableName
Section 59.5: Returns size and fragmentation indexes
sys.dm_db_index_physical_stats (
{ database_id | NULL | 0 | DEFAULT } , { object_id | NULL | 0 | DEFAULT } , { index_id | NULL | 0 | -1 | DEFAULT }
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, { partition_number | NULL | 0 | DEFAULT } , { mode | NULL | DEFAULT } )
Sample :
SELECT * FROM sys.dm_db_index_physical_stats
(DB_ID(N'DBName'), OBJECT_ID(N'IX_NonClustered '), NULL, NULL , 'DETAILED');
Section 59.6: Reorganize and rebuild index
avg_fragmentation_in_percent value Corrective statement >5% and < = 30% REORGANIZE >30% REBUILD
ALTER INDEX IX_NonClustered ON tableName REORGANIZE;
ALTER INDEX ALL ON Production.Product
REBUILD WITH (FILLFACTOR = 80, SORT_IN_TEMPDB = ON,
STATISTICS_NORECOMPUTE = ON);
Section 59.7: Rebuild or reorganize all indexes on a table
Rebuilding indexes is done using the following statement
ALTER INDEX All ON tableName REBUILD;
This drops the index and recreates it, removing fragementation, reclaims disk space and reorders index pages.
One can also reorganize an index using
ALTER INDEX All ON tableName REORGANIZE;
which will use minimal system resources and defragments the leaf level of clustered and nonclustered indexes on tables and views by physically reordering the leaf-level pages to match the logical, left to right, order of the leaf nodes
Section 59.8: Rebuild all index database
EXEC sp_MSForEachTable 'ALTER INDEX ALL ON ? REBUILD'
Section 59.9: Index on view
CREATE VIEW View_Index02 WITH SCHEMABINDING AS SELECT c.CompanyName, o.OrderDate, o.OrderID, od.ProductID
FROM dbo.Customers C
INNER JOIN dbo.orders O ON c.CustomerID=o.CustomerID
INNER JOIN dbo.[Order Details] od ON o.OrderID=od.OrderID GO
CREATE UNIQUE CLUSTERED INDEX IX1 ON View_Index02(OrderID, ProductID)
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Section 59.10: Index investigations
You could use "SP_HELPINDEX Table_Name", but Kimberly Tripp has a stored procedure (that can be found here), which is better example, as it shows more about the indexes, including columns and filter definition, for example: Usage:
USE Adventureworks EXEC sp_SQLskills_SQL2012_helpindex 'dbo.Product'
Alternatively, Tibor Karaszi has a stored procedure (found here). The later will show information on index usage too, and optionally provide a list of index suggestions. Usage:
USE Adventureworks EXEC sp_indexinfo 'dbo.Product'
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Chapter 60: Full-Text Indexing
Section 60.1: A. Creating a unique index, a full-text catalog, and a full-text index
The following example creates a unique index on the JobCandidateID column of the HumanResources.JobCandidate table of the AdventureWorks2012 sample database. The example then creates a default full-text catalog, ft. Finally, the example creates a full-text index on the Resume column, using the ft catalog and the system stoplist.
USE AdventureWorks2012; GO CREATE UNIQUE INDEX ui_ukJobCand ON HumanResources.JobCandidate(JobCandidateID); CREATE FULLTEXT CATALOG ft AS DEFAULT; CREATE FULLTEXT INDEX ON HumanResources.JobCandidate(Resume)
KEY INDEX ui_ukJobCand WITH STOPLIST = SYSTEM; GO
https://www.simple-talk.com/sql/learn-sql-server/understanding-full-text-indexing-in-sql-server/
https://msdn.microsoft.com/en-us/library/cc879306.aspx
https://msdn.microsoft.com/en-us/library/ms142571.aspx
Section 60.2: Creating a full-text index on several table columns
USE AdventureWorks2012; GO CREATE FULLTEXT CATALOG production_catalog; GO CREATE FULLTEXT INDEX ON Production.ProductReview
(
ReviewerName
Language 1033, EmailAddress
Language 1033, Comments
Language 1033 )
KEY INDEX PK_ProductReview_ProductReviewID
ON production_catalog; GO
Section 60.3: Creating a full-text index with a search property list without populating it
USE AdventureWorks2012; GO CREATE FULLTEXT INDEX ON Production.Document
( Title
Language 1033, DocumentSummary
Language 1033, Document
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TYPE COLUMN FileExtension Language 1033 ) KEY INDEX PK_Document_DocumentID
WITH STOPLIST = SYSTEM, SEARCH PROPERTY LIST = DocumentPropertyList, CHANGE_TRACKING OFF, NO POPULATION;
GO
And populating it later with
ALTER FULLTEXT INDEX ON Production.Document SET CHANGE_TRACKING AUTO; GO
Section 60.4: Full-Text Search
SELECT product_id FROM products WHERE CONTAINS(product_description, ”Snap Happy 100EZ” OR FORMSOF(THESAURUS,’Snap Happy’) OR ‘100EZ’)
AND product_cost < 200 ;
SELECT candidate_name,SSN FROM candidates WHERE CONTAINS(candidate_resume,”SQL Server”) AND candidate_division =DBA;
For more and detailed info https://msdn.microsoft.com/en-us/library/ms142571.aspx
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Chapter 61: Trigger
A trigger is a special type of stored procedure, which is executed automatically after an event occurs. There are two types of triggers: Data Definition Language Triggers and Data Manipulation Language Triggers.
It is usually bound to a table and fires automatically. You cannot explicitly call any trigger.
Section 61.1: DML Triggers
DML Triggers are fired as a response to dml statements (insert, update or delete). A dml trigger can be created to address one or more dml events for a single table or view. This means that a single dml trigger can handle inserting, updating and deleting records from a specific table or view, but in can only handle data being changed on that single table or view.
DML Triggers provides access to inserted and deleted tables that holds information about the data that was / will be affected by the insert, update or delete statement that fired the trigger.
Note that DML triggers are statement based, not row based. This means that if the statement effected more then one row, the inserted or deleted tables will contain more then one row.
Examples:
CREATE TRIGGER tblSomething_InsertOrUpdate ON tblSomething FOR INSERT AS
INSERT INTO tblAudit (TableName, RecordId, Action) SELECT 'tblSomething', Id, 'Inserted' FROM Inserted
GO
CREATE TRIGGER tblSomething_InsertOrUpdate ON tblSomething FOR UPDATE AS
INSERT INTO tblAudit (TableName, RecordId, Action) SELECT 'tblSomething', Id, 'Updated' FROM Inserted
GO
CREATE TRIGGER tblSomething_InsertOrUpdate ON tblSomething FOR DELETE AS
INSERT INTO tblAudit (TableName, RecordId, Action) SELECT 'tblSomething', Id, 'Deleted' FROM Deleted
GO
All the examples above will add records to tblAudit whenever a record is added, deleted or updated in tblSomething.
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Section 61.2: Types and classifications of Trigger
In SQL Server, there are two categories of triggers: DDL Triggers and DML Triggers.
DDL Triggers are fired in response to Data Definition Language (DDL) events. These events primarily correspond to Transact-SQL statements that start with the keywords CREATE, ALTER and DROP.
DML Triggers are fired in response to Data Manipulation Language (DML) events. These events corresponds to Transact-SQL statements that start with the keywords INSERT, UPDATE and DELETE.
DML triggers are classified into two main types:
After Triggers (for triggers) 1.
AFTER INSERT Trigger. AFTER UPDATE Trigger. AFTER DELETE Trigger.
Instead of triggers 2.
INSTEAD OF INSERT Trigger. INSTEAD OF UPDATE Trigger. INSTEAD OF DELETE Trigger.
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Chapter 62: Cursors
Section 62.1: Basic Forward Only Cursor
Normally you would want to avoid using cursors as they can have negative impacts on performance. However in some special cases you may need to loop through your data record by record and perform some action.
DECLARE @orderId AS INT
-- here we are creating our cursor, as a local cursor and only allowing -- forward operations DECLARE rowCursor CURSOR LOCAL FAST_FORWARD FOR
-- this is the query that we want to loop through record by record SELECT [OrderId] FROM [dbo].[Orders]
-- first we need to open the cursor OPEN rowCursor
-- now we will initialize the cursor by pulling the first row of data, in this example the [OrderId] column, -- and storing the value into a variable called @orderId FETCH NEXT FROM rowCursor INTO @orderId
-- start our loop and keep going until we have no more records to loop through WHILE @@FETCH_STATUS = 0 BEGIN
PRINT @orderId
-- this is important, as it tells SQL Server to get the next record and store the [OrderId] column value into the @orderId variable
FETCH NEXT FROM rowCursor INTO @orderId
END
-- this will release any memory used by the cursor CLOSE rowCursor DEALLOCATE rowCursor
Section 62.2: Rudimentary cursor syntax
A simple cursor syntax, operating on a few example test rows:
/* Prepare test data */ DECLARE @test_table TABLE (
Id INT, Val VARCHAR(100) ); INSERT INTO @test_table(Id, Val) VALUES
(1, 'Foo'), (2, 'Bar'), (3, 'Baz'); /* Test data prepared */
/* Iterator variable @myId, for example sake */
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DECLARE @myId INT;
/* Cursor to iterate rows and assign values to variables */ DECLARE myCursor CURSOR FOR
SELECT Id FROM @test_table;
/* Start iterating rows */ OPEN myCursor; FETCH NEXT FROM myCursor INTO @myId;
/* @@FETCH_STATUS global variable will be 1 / true until there are no more rows to fetch */ WHILE @@FETCH_STATUS = 0 BEGIN
/* Write operations to perform in a loop here. Simple SELECT used for example */ SELECT Id, Val FROM @test_table WHERE Id = @myId;
/* Set variable(s) to the next value returned from iterator; this is needed otherwise the cursor will loop infinitely. */
FETCH NEXT FROM myCursor INTO @myId; END /* After all is done, clean up */ CLOSE myCursor; DEALLOCATE myCursor;
Results from SSMS. Note that these are all separate queries, they are in no way unified. Notice how the query engine processes each iteration one by one instead of as a set.
Id Val 1 Foo (1 row(s) affected)
Id Val 2 Bar
(1 row(s) affected)
Id Val 3 Baz
(1 row(s) affected)
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Chapter 63: Transaction isolation levels
Section 63.1: Read Committed
Version ≥ SQL Server 2008 R2
SET TRANSACTION ISOLATION LEVEL READ COMMITTED
This isolation level is the 2nd most permissive. It prevents dirty reads. The behavior of READ COMMITTED depends on the setting of the READ_COMMITTED_SNAPSHOT:
If set to OFF (the default setting) the transaction uses shared locks to prevent other transactions from modifying rows used by the current transaction, as well as block the current transaction from reading rows modified by other transactions.
If set to ON, the READCOMMITTEDLOCK table hint can be used to request shared locking instead of row versioning for transactions running in READ COMMITTED mode.
Note: READ COMMITTED is the default SQL Server behavior.
Section 63.2: What are "dirty reads"?
Dirty reads (or uncommitted reads) are reads of rows which are being modified by an open transaction.
This behavior can be replicated by using 2 separate queries: one to open a transaction and write some data to a table without committing, the other to select the data to be written (but not yet committed) with this isolation level.
Query 1 - Prepare a transaction but do not finish it:
CREATE TABLE dbo.demo (
col1 INT, col2 VARCHAR(255) ); GO --This row will get committed normally: BEGIN TRANSACTION;
INSERT INTO dbo.demo(col1, col2) VALUES (99, 'Normal transaction'); COMMIT TRANSACTION; --This row will be "stuck" in an open transaction, causing a dirty read BEGIN TRANSACTION;
INSERT INTO dbo.demo(col1, col2) VALUES (42, 'Dirty read'); --Do not COMMIT TRANSACTION or ROLLBACK TRANSACTION here
Query 2 - Read the rows including the open transaction:
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED; SELECT * FROM dbo.demo;
Returns:
col1 col2 ----------- --------------------------------------- 99 Normal transaction
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42 Dirty read
P.S.: Don't forget to clean up this demo data:
COMMIT TRANSACTION; DROP TABLE dbo.demo; GO
Section 63.3: Read Uncommitted
Version ≥ SQL Server 2008 R2
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
This is the most permissive isolation level, in that it does not cause any locks at all. It specifies that statements can read all rows, including rows that have been written in transactions but not yet committed (i.e., they are still in transaction). This isolation level can be subject to "dirty reads".
Section 63.4: Repeatable Read
Version ≥ SQL Server 2008 R2
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ
This transaction isolation level is slightly less permissive than READ COMMITTED, in that shared locks are placed on all data read by each statement in the transaction and are held until the transaction completes, as opposed to being released after each statement.
Note: Use this option only when necessary, as it is more likely to cause database performance degradation as well as deadlocks than READ COMMITTED.
Section 63.5: Snapshot
Version ≥ SQL Server 2008 R2
SET TRANSACTION ISOLATION LEVEL SNAPSHOT
Specifies that data read by any statement in a transaction will be the transactionally consistent version of the data that existed at the start of the transaction, i.e., it will only read data that has been committed prior to the transaction starting.
SNAPSHOT transactions do not request or cause any locks on the data that is being read, as it is only reading the version (or snapshot) of the data that existed at the time the transaction began.
A transaction running in SNAPSHOT isolation level read only its own data changes while it is running. For example, a transaction could update some rows and then read the updated rows, but that change will only be visible to the current transaction until it is committed.
Note: The ALLOW_SNAPSHOT_ISOLATION database option must be set to ON before the SNAPSHOT isolation level can be used.
Section 63.6: Serializable
Version ≥ SQL Server 2008 R2
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SET TRANSACTION ISOLATION LEVEL SERIALIZEABLE
This isolation level is the most restrictive. It requests range locks the range of key values that are read by each statement in the transaction. This also means that INSERT statements from other transactions will be blocked if the rows to be inserted are in the range locked by the current transaction.
This option has the same effect as setting HOLDLOCK on all tables in all SELECT statements in a transaction.
Note: This transaction isolation has the lowest concurrency and should only be used when necessary.
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Chapter 64: Advanced options
Section 64.1: Enable and show advanced options
Exec sp_configure 'show advanced options' ,1 RECONFIGURE GO -- Show all configure sp_configure
Section 64.2: Enable backup compression default
Exec sp_configure 'backup compression default',1 GO RECONFIGURE;
Section 64.3: Enable cmd permission
EXEC sp_configure 'xp_cmdshell', 1 GO RECONFIGURE
Section 64.4: Set default fill factor percent
sp_configure 'fill factor', 100; GO RECONFIGURE;
The server must be restarted before the change can take effect.
Section 64.5: Set system recovery interval
USE master; GO -- Set recovery every 3 min EXEC sp_configure 'recovery interval', '3'; RECONFIGURE WITH OVERRIDE;
Section 64.6: Set max server memory size
USE master EXEC sp_configure 'max server memory (MB)', 64 RECONFIGURE WITH OVERRIDE
Section 64.7: Set number of checkpoint tasks
EXEC sp_configure "number of checkpoint tasks", 4
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Chapter 65: Migration
Section 65.1: How to generate migration scripts
Click Right Mouse on Database you want to migrate then -> Tasks -> Generate Scripts... 1.
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Wizard will open click Next then chose objects you want to migrate and click Next again, then click Advanced 2.
scroll a bit down and in Types of data to script choose Schema and data (unless you want only structures)
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Click couple more times Next and Finish and you should have your database scripted in .sql file. 3.
run .sql file on your new server, and you should be done. 4.
Chapter 66: Table Valued Parameters
Section 66.1: Using a table valued parameter to insert multiple rows to a table
First, define a used defined table type to use:
CREATE TYPE names as TABLE (
FirstName varchar(10), LastName varchar(10) ) GO
Create the stored procedure:
CREATE PROCEDURE prInsertNames (
@Names dbo.Names READONLY -- Note: You must specify the READONLY ) AS
INSERT INTO dbo.TblNames (FirstName, LastName) SELECT FirstName, LastName FROM @Names GO
Executing the stored procedure:
DECLARE @names dbo.Names INSERT INTO @Names VALUES ('Zohar', 'Peled'), ('First', 'Last')
EXEC dbo.prInsertNames @Names
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Chapter 67: DBMAIL
Section 67.1: Send simple email
This code sends a simple text-only email to recipient@someaddress.com
EXEC msdb.dbo.sp_send_dbmail
@profile_name = 'The Profile Name', @recipients = 'recipient@someaddress.com', @body = 'This is a simple email sent from SQL Server.', @subject = 'Simple email'
Section 67.2: Send results of a query
This attaches the results of the query SELECT * FROM Users and sends it to recipient@someaddress.com
EXEC msdb.dbo.sp_send_dbmail
@profile_name = 'The Profile Name', @recipients = 'recipient@someaddress.com', @query = 'SELECT * FROM Users', @subject = 'List of users', @attach_query_result_as_file = 1;
Section 67.3: Send HTML email
HTML content must be passed to sp_send_dbmail
Version ≥ SQL Server 2012
DECLARE @html VARCHAR(MAX); SET @html = CONCAT (
'<html><body>', '<h1>Some Header Text</h1>', '<p>Some paragraph text</p>', '</body></html>' )
Version < SQL Server 2012
DECLARE @html VARCHAR(MAX); SET @html =
'<html><body>' + '<h1>Some Header Text</h1>' + '<p>Some paragraph text</p>' + '</body></html>';
Then use the @html variable with the @body argument. The HTML string can also be passed directly to @body, although it may make the code harder to read.
EXEC msdb.dbo.sp_send_dbmail
@recipients='recipient@someaddress.com', @subject = 'Some HTML content', @body = @html, @body_format = 'HTML';
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Chapter 68: In-Memory OLTP (Hekaton)
Section 68.1: Declare Memory-Optimized Table Variables
For faster performance you can memory-optimize your table variable. Here is the T-SQL for a traditional table variable:
DECLARE @tvp TABLE (
col1 INT NOT NULL , Col2 CHAR(10) );
To define memory-optimized variables, you must first create a memory-optimized table type and then declare a variable from it:
CREATE TYPE dbo.memTypeTable AS TABLE (
Col1 INT NOT NULL INDEX ix1, Col2 CHAR(10) ) WITH
(MEMORY_OPTIMIZED = ON);
Then we can use the table type like this:
DECLARE @tvp memTypeTable insert INTO @tvp values (1,'1'),(2,'2'),(3,'3'),(4,'4'),(5,'5'),(6,'6')
SELECT * FROM @tvp
Result:
Col1 Col2 1 1 2 2 3 3 4 4 5 5 6 6
Section 68.2: Create Memory Optimized Table
-- Create demo database CREATE DATABASE SQL2016_Demo
ON PRIMARY (
NAME = N'SQL2016_Demo', FILENAME = N'C:\Dump\SQL2016_Demo.mdf', SIZE = 5120KB, FILEGROWTH = 1024KB ) LOG ON (
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NAME = N'SQL2016_Demo_log', FILENAME = N'C:\Dump\SQL2016_Demo_log.ldf', SIZE = 1024KB, FILEGROWTH = 10% ) GO
use SQL2016_Demo go
-- Add Filegroup by MEMORY_OPTIMIZED_DATA type ALTER DATABASE SQL2016_Demo
ADD FILEGROUP MemFG CONTAINS MEMORY_OPTIMIZED_DATA GO
--Add a file to defined filegroup ALTER DATABASE SQL2016_Demo ADD FILE
(
NAME = MemFG_File1, FILENAME = N'C:\Dump\MemFG_File1' -- your file path, check directory exist before executing this code ) TO FILEGROUP MemFG GO
--Object Explorer -- check database created GO
-- create memory optimized table 1 CREATE TABLE dbo.MemOptTable1 (
Column1 INT NOT NULL, Column2 NVARCHAR(4000) NULL, SpidFilter SMALLINT NOT NULL DEFAULT (@@spid),
INDEX ix_SpidFiler NONCLUSTERED (SpidFilter), INDEX ix_SpidFilter HASH (SpidFilter) WITH (BUCKET_COUNT = 64),
CONSTRAINT CHK_soSessionC_SpidFilter
CHECK ( SpidFilter = @@spid ), )
WITH
(MEMORY_OPTIMIZED = ON,
DURABILITY = SCHEMA_AND_DATA); --or DURABILITY = SCHEMA_ONLY go
-- create memory optimized table 2 CREATE TABLE MemOptTable2 (
ID INT NOT NULL PRIMARY KEY NONCLUSTERED HASH WITH (BUCKET_COUNT = 10000), FullName NVARCHAR(200) NOT NULL, DateAdded DATETIME NOT NULL ) WITH (MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA) GO
Section 68.3: Show created .dll files and tables for Memory Optimized Tables
SELECT
OBJECT_ID('MemOptTable1') AS MemOptTable1_ObjectID,
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OBJECT_ID('MemOptTable2') AS MemOptTable2_ObjectID GO
SELECT
name,description FROM sys.dm_os_loaded_modules WHERE name LIKE '%XTP%' GO
Show all Memory Optimized Tables:
SELECT
name,type_desc,durability_desc,Is_memory_Optimized FROM sys.tables
WHERE Is_memory_Optimized = 1 GO
Section 68.4: Create Memory Optimized System-Versioned Temporal Table
CREATE TABLE [dbo].[MemOptimizedTemporalTable] (
[BusinessDocNo] [bigint] NOT NULL, [ProductCode] [int] NOT NULL, [UnitID] [tinyint] NOT NULL, [PriceID] [tinyint] NOT NULL, [SysStartTime] [datetime2](7) GENERATED ALWAYS AS ROW START NOT NULL, [SysEndTime] [datetime2](7) GENERATED ALWAYS AS ROW END NOT NULL, PERIOD FOR SYSTEM_TIME ([SysStartTime], [SysEndTime]),
CONSTRAINT [PK_MemOptimizedTemporalTable] PRIMARY KEY NONCLUSTERED (
[BusinessDocNo] ASC, [ProductCode] ASC ) ) WITH (
MEMORY_OPTIMIZED = ON , DURABILITY = SCHEMA_AND_DATA, -- Memory Optimized Option ON SYSTEM_VERSIONING = ON (HISTORY_TABLE = [dbo].[MemOptimizedTemporalTable_History] , DATA_CONSISTENCY_CHECK = ON ) )
more information
Section 68.5: Memory-Optimized Table Types and Temp tables
For example, this is traditional tempdb-based table type:
CREATE TYPE dbo.testTableType AS TABLE (
col1 INT NOT NULL, col2 CHAR(10) );
To memory-optimize this table type simply add the option memory_optimized=on, and add an index if there is none on the original type:
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CREATE TYPE dbo.testTableType AS TABLE (
col1 INT NOT NULL, col2 CHAR(10) )WITH (MEMORY_OPTIMIZED=ON);
Global temporary table is like this:
CREATE TABLE ##tempGlobalTabel (
Col1 INT NOT NULL , Col2 NVARCHAR(4000) );
Memory-optimized global temporary table:
CREATE TABLE dbo.tempGlobalTabel (
Col1 INT NOT NULL INDEX ix NONCLUSTERED, Col2 NVARCHAR(4000) )
WITH
(MEMORY_OPTIMIZED = ON,
DURABILITY = SCHEMA_ONLY);
To memory-optimize global temp tables (##temp):
Create a new SCHEMA_ONLY memory-optimized table with the same schema as the global ##temp table 1.
Ensure the new table has at least one index Change all references to ##temp in your Transact-SQL statements to the new memory-optimized table temp 2. Replace the DROP TABLE ##temp statements in your code with DELETE FROM temp, to clean up the contents 3. Remove the CREATE TABLE ##temp statements from your code – these are now redundant 4.
more information
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Chapter 69: Temporal Tables
Section 69.1: CREATE Temporal Tables
CREATE TABLE dbo.Employee (
[EmployeeID] int NOT NULL PRIMARY KEY CLUSTERED , [Name] nvarchar(100) NOT NULL , [Position] varchar(100) NOT NULL , [Department] varchar(100) NOT NULL , [Address] nvarchar(1024) NOT NULL , [AnnualSalary] decimal (10,2) NOT NULL , [ValidFrom] datetime2 (2) GENERATED ALWAYS AS ROW START , [ValidTo] datetime2 (2) GENERATED ALWAYS AS ROW END , PERIOD FOR SYSTEM_TIME (ValidFrom, ValidTo) ) WITH (SYSTEM_VERSIONING = ON (HISTORY_TABLE = dbo.EmployeeHistory));
INSERTS: On an INSERT, the system sets the value for the ValidFrom column to the begin time of the current transaction (in the UTC time zone) based on the system clock and assigns the value for the ValidTo column to the maximum value of 9999-12-31. This marks the row as open.
UPDATES: On an UPDATE, the system stores the previous value of the row in the history table and sets the value for the ValidTo column to the begin time of the current transaction (in the UTC time zone) based on the system clock. This marks the row as closed, with a period recorded for which the row was valid. In the current table, the row is updated with its new value and the system sets the value for the ValidFrom column to the begin time for the transaction (in the UTC time zone) based on the system clock. The value for the updated row in the current table for the ValidTo column remains the maximum value of 9999-12-31.
DELETES: On a DELETE, the system stores the previous value of the row in the history table and sets the value for the ValidTo column to the begin time of the current transaction (in the UTC time zone) based on the system clock. This marks the row as closed, with a period recorded for which the previous row was valid. In the current table, the row is removed. Queries of the current table will not return this row. Only queries that deal with history data return data for which a row is closed.
MERGE: On a MERGE, the operation behaves exactly as if up to three statements (an INSERT, an UPDATE, and/or a DELETE) executed, depending on what is specified as actions in the MERGE statement.
Tip : The times recorded in the system datetime2 columns are based on the begin time of the transaction itself. For example, all rows inserted within a single transaction will have the same UTC time recorded in the column corresponding to the start of the SYSTEM_TIME period.
Section 69.2: FOR SYSTEM_TIME ALL
Returns the union of rows that belong to the current and the history table.
SELECT * FROM Employee
FOR SYSTEM_TIME ALL
Section 69.3: Creating a Memory-Optimized System-Versioned Temporal Table and cleaning up the SQL Server history table
Creating a temporal table with a default history table is a convenient option when you want to control naming and
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still rely on system to create history table with default configuration. In the example below, a new system-versioned memory-optimized temporal table linked to a new disk-based history table.
CREATE SCHEMA History GO CREATE TABLE dbo.Department (
DepartmentNumber char(10) NOT NULL PRIMARY KEY NONCLUSTERED, DepartmentName varchar(50) NOT NULL, ManagerID int NULL, ParentDepartmentNumber char(10) NULL, SysStartTime datetime2 GENERATED ALWAYS AS ROW START HIDDEN NOT NULL, SysEndTime datetime2 GENERATED ALWAYS AS ROW END HIDDEN NOT NULL, PERIOD FOR SYSTEM_TIME (SysStartTime,SysEndTime) ) WITH
(
MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA, SYSTEM_VERSIONING = ON ( HISTORY_TABLE = History.DepartmentHistory ) );
Cleaning up the SQL Server history table Over time the history table can grow significantly. Since inserting, updating or deleting data from the history table are not allowed, the only way to clean up the history table is first to disable system versioning:
ALTER TABLE dbo.Employee SET (SYSTEM_VERSIONING = OFF); GO
Delete unnecessary data from the history table:
DELETE FROM dbo.EmployeeHistory WHERE EndTime <= '2017-01-26 14:00:29';
and then re-enable system versioning:
ALTER TABLE dbo.Employee SET (SYSTEM_VERSIONING = ON (HISTORY_TABLE = [dbo].[EmployeeHistory], DATA_CONSISTENCY_CHECK = ON));
Cleaning the history table in Azure SQL Databases is a little different, since Azure SQL databases have built-in support for cleaning of the history table. First, temporal history retention cleanup need to be enable on a database level:
ALTER DATABASE CURRENT SET TEMPORAL_HISTORY_RETENTION ON GO
Then set the retention period per table:
ALTER TABLE dbo.Employee SET (SYSTEM_VERSIONING = ON (HISTORY_RETENTION_PERIOD = 90 DAYS));
This will delete all data in the history table older than 90 days. SQL Server 2016 on-premise databases do not support TEMPORAL_HISTORY_RETENTION and HISTORY_RETENTION_PERIOD and either of the above two queries are executed on the SQL Server 2016 on-premise databases the following errors will occur.
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For TEMPORAL_HISTORY_RETENTION error will be:
Msg 102, Level 15, State 6, Line 34
Incorrect syntax near ‘TEMPORAL_HISTORY_RETENTION’.
For HISTORY_RETENTION_PERIOD error will be:
Msg 102, Level 15, State 1, Line 39
Incorrect syntax near ‘HISTORY_RETENTION_PERIOD’.
Section 69.4: FOR SYSTEM_TIME BETWEEN <start_date_time> AND <end_date_time>
Same as above in the FOR SYSTEM_TIME FROM <start_date_time>TO <end_date_time> description, except the table of rows returned includes rows that became active on the upper boundary defined by the <end_date_time> endpoint.
SELECT * FROM Employee
FOR SYSTEM_TIME BETWEEN '2015-01-01' AND '2015-12-31'
Section 69.5: FOR SYSTEM_TIME FROM <start_date_time> TO <end_date_time>
Returns a table with the values for all row versions that were active within the specified time range, regardless of whether they started being active before the <start_date_time> parameter value for the FROM argument or ceased being active after the <end_date_time> parameter value for the TO argument. Internally, a union is performed between the temporal table and its history table and the results are filtered to return the values for all row versions that were active at any time during the time range specified. Rows that became active exactly on the lower boundary defined by the FROM endpoint are included and records that became active exactly on the upper boundary defined by the TO endpoint are not included.
SELECT * FROM Employee
FOR SYSTEM_TIME FROM '2015-01-01' TO '2015-12-31'
Section 69.6: FOR SYSTEM_TIME CONTAINED IN (<start_date_time> , <end_date_time>)
Returns a table with the values for all row versions that were opened and closed within the specified time range defined by the two datetime values for the CONTAINED IN argument. Rows that became active exactly on the lower boundary or ceased being active exactly on the upper boundary are included.
SELECT * FROM Employee
FOR SYSTEM_TIME CONTAINED IN ('2015-04-01', '2015-09-25')
Section 69.7: How do I query temporal data?
SELECT * FROM Employee
FOR SYSTEM_TIME
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BETWEEN '2014-01-01 00:00:00.0000000' AND '2015-01-01 00:00:00.0000000'
WHERE EmployeeID = 1000 ORDER BY ValidFrom;
Section 69.8: Return actual value specified point in time(FOR SYSTEM_TIME AS OF <date_time>)
Returns a table with a rows containing the values that were actual (current) at the specified point in time in the past.
SELECT * FROM Employee
FOR SYSTEM_TIME AS OF '2016-08-06 08:32:37.91'
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Chapter 70: Use of TEMP Table
Section 70.1: Dropping temp tables
Temp tables must have unique IDs (within the session, for local temp tables, or within the server, for global temp tables). Trying to create a table using a name that already exists will return the following error:
There is already an object named '#tempTable' in the database.
If your query produces temp tables, and you want to run it more than once, you will need to drop the tables before trying to generate them again. The basic syntax for this is:
drop table #tempTable
Trying to execute this syntax before the table exists (e.g. on the first run of your syntax) will cause another error:
Cannot drop the table '#tempTable', because it does not exist or you do not have permission.
To avoid this, you can check to see if the table already exists before dropping it, like so:
IF OBJECT_ID ('tempdb..#tempTable', 'U') is not null DROP TABLE #tempTable
Section 70.2: Local Temp Table
Will be available till the current connection persists for the user.
Automatically deleted when the user disconnects.
The name should start with # (#temp)
CREATE TABLE #LocalTempTable(
StudentID int, StudentName varchar(50), StudentAddress varchar(150))
insert into #LocalTempTable values ( 1, 'Ram','India');
select * from #LocalTempTable
After executing all these statements if we close the query window and open it again and try inserting and select it will show an error message
“Invalid object name #LocalTempTable”
Section 70.3: Global Temp Table
Will start with ## (##temp).
Will be deleted only if user disconnects all connections.
It behaves like a permanent table.
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CREATE TABLE ##NewGlobalTempTable( StudentID int, StudentName varchar(50), StudentAddress varchar(150))
Insert Into ##NewGlobalTempTable values ( 1,'Ram','India'); Select * from ##NewGlobalTempTable
Note: These are viewable by all users of the database, irrespective of permissions level.
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Chapter 71: Scheduled Task or Job
SQL Server Agent uses SQL Server to store job information. Jobs contain one or more job steps. Each step contains its own task,i.e: backing up a database. SQL Server Agent can run a job on a schedule, in response to a specific event, or on demand.
Section 71.1: Create a scheduled Job
Create a Job
To add a job first we have to use a stored procedure named sp_add_job
USE msdb ; GO EXEC dbo.sp_add_job @job_name = N'Weekly Job' ; -- the job name
Then we have to add a job step using a stored procedure named sp_add_jobStep
EXEC sp_add_jobstep @job_name = N'Weekly Job', -- Job name to add a step @step_name = N'Set database to read only', -- step name @subsystem = N'TSQL', -- Step type @command = N'ALTER DATABASE SALES SET READ_ONLY', -- Command @retry_attempts = 5, --Number of attempts @retry_interval = 5 ; -- in minutes
Target the job to a server
EXEC dbo.sp_add_jobserver @job_name = N'Weekly Sales Data Backup', @server_name = 'MyPC\data; -- Default is LOCAL GO
Create a schedule using SQL
To Create a schedule we have to use a system stored procedure called sp_add_schedule
USE msdb GO
EXEC sp_add_schedule
@schedule_name = N'NightlyJobs' , -- specify the schedule name @freq_type = 4, -- A value indicating when a job is to be executed (4) means Daily @freq_interval = 1, -- The days that a job is executed and depends on the value of `freq_type`.
@active_start_time = 010000 ; -- The time on which execution of a job can begin GO
There are more parameters that can be used with sp_add_schedule you can read more about in the the link provided above.
Attaching schedule to a JOB
To attach a schedule to an SQL agent job you have to use a stored procedure called sp_attach_schedule
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-- attaches the schedule to the job BackupDatabase EXEC sp_attach_schedule
@job_name = N'BackupDatabase', -- The job name to attach with @schedule_name = N'NightlyJobs' ; -- The schedule name GO
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Chapter 72: Isolation levels and locking
Section 72.1: Examples of setting the isolation level
Example of setting the isolation level:
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED; SELECT * FROM Products WHERE ProductId=1; SET TRANSACTION ISOLATION LEVEL REPEATABLE READ; --return to the default one
READ UNCOMMITTED - means that a query in the current transaction can't access the modified data from 1.
another transaction that is not yet committed - no dirty reads! BUT, nonrepeatable reads and phantom reads are possible, because data can still be modified by other transactions.
REPEATABLE READ - means that a query in the the current transaction can't access the modified data from 2.
another transaction that is not yet committed - no dirty reads! No other transactions can modify data being read by the current transaction until it is completed, which eliminates NONREPEATABLE reads. BUT, if another transaction inserts NEW ROWS and the query is executed more then once, phantom rows can appear starting the second read (if it matches the where statement of the query).
SNAPSHOT - only able to return data that exists at the beginning of the query. Ensures consistency of the data. 3.
It prevents dirty reads, nonrepeatable reads and phantom reads. To use that - DB configurationis required:
ALTER DATABASE DBTestName SET ALLOW_SNAPSHOT_ISOLATION ON;GO; SET TRANSACTION ISOLATION LEVEL SNAPSHOT;
READ COMMITTED - default isolation of the SQL server. It prevents reading the data that is changed by another 4. transaction until committed. It uses shared locking and row versioning on the tables which prevents dirty reads. It depends on DB configuration READ_COMMITTED_SNAPSHOT - if enabled - row versioning is used. to enable - use this:
ALTER DATABASE DBTestName SET ALLOW_SNAPSHOT_ISOLATION ON;GO; SET TRANSACTION ISOLATION LEVEL READ COMMITTED; --return to the default one
SERIALIZABLE - uses physical locks that are acquired and held until end of the transaction, which prevents 5. dirty reads, phantom reads, nonrepeatable reads. BUT, it impacts on the performance of the DataBase, because the concurrent transactions are serialized and are being executed one by one.
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE ;
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Chapter 73: Sorting/ordering rows
Section 73.1: Basics
First, let's setup the example table.
-- Create a table as an example CREATE TABLE SortOrder (
ID INT IDENTITY PRIMARY KEY, [Text] VARCHAR(256) ) GO
-- Insert rows into the table INSERT INTO SortOrder ([Text]) SELECT ('Lorem ipsum dolor sit amet, consectetur adipiscing elit') UNION ALL SELECT ('Pellentesque eu dapibus libero') UNION ALL SELECT ('Vestibulum et consequat est, ut hendrerit ligula') UNION ALL SELECT ('Suspendisse sodales est congue lorem euismod, vel facilisis libero pulvinar') UNION ALL SELECT ('Suspendisse lacus est, aliquam at varius a, fermentum nec mi') UNION ALL SELECT ('Praesent tincidunt tortor est, nec consequat dolor malesuada quis') UNION ALL SELECT ('Quisque at tempus arcu') GO
Remember that when retrieving data, if you don't specify a row ordering clause (ORDER BY) SQL server does not guarantee the sorting (order of the columns) at any time. Really, at any time. And there's no point arguing about that, it has been shown literally thousands of times and all over the internet.
No ORDER BY == no sorting. End of story.
-- It may seem the rows are sorted by identifiers, -- but there is really no way of knowing if it will always work. -- And if you leave it like this in production, Murphy gives you a 100% that it won't. SELECT * FROM SortOrder GO
There are two directions data can be ordered by:
ascending (moving upwards), using ASC descending (moving downwards), using DESC
-- Ascending - upwards SELECT * FROM SortOrder ORDER BY ID ASC GO
-- Ascending is default SELECT * FROM SortOrder ORDER BY ID GO
-- Descending - downwards SELECT * FROM SortOrder ORDER BY ID DESC GO
When ordering by the textual column ((n)char or (n)varchar), pay attention that the order respects the collation. For more information on collation look up for the topic.
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Ordering and sorting of data can consume resources. This is where properly created indexes come handy. For more information on indexes look up for the topic.
There is a possibility to pseudo-randomize the order of rows in your resultset. Just force the ordering to appear nondeterministic.
SELECT * FROM SortOrder ORDER BY CHECKSUM(NEWID()) GO
Ordering can be remembered in a stored procedure, and that's the way you should do it if it is the last step of manipulating the rowset before showing it to the end user.
CREATE PROCEDURE GetSortOrder AS
SELECT * FROM SortOrder ORDER BY ID DESC GO
EXEC GetSortOrder GO
There is a limited (and hacky) support for ordering in the SQL Server views as well, but be encouraged NOT to use it.
/* This may or may not work, and it depends on the way
your SQL Server and updates are installed */ CREATE VIEW VwSortOrder1 AS
SELECT TOP 100 PERCENT * FROM SortOrder ORDER BY ID DESC GO
SELECT * FROM VwSortOrder1 GO
-- This will work, but hey... should you really use it? CREATE VIEW VwSortOrder2 AS
SELECT TOP 99999999 * FROM SortOrder ORDER BY ID DESC GO
SELECT * FROM VwSortOrder2 GO
For ordering you can either use column names, aliases or column numbers in your ORDER BY.
SELECT * FROM SortOrder ORDER BY [Text]
-- New resultset column aliased as 'Msg', feel free to use it for ordering SELECT ID, [Text] + ' (' + CAST(ID AS nvarchar(10)) + ')' AS Msg FROM SortOrder ORDER BY Msg
-- Can be handy if you know your tables, but really NOT GOOD for production
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SELECT * FROM SortOrder ORDER BY 2
I advise against using the numbers in your code, except if you want to forget about it the moment after you execute it.
Section 73.2: Order by Case
If you want to sort your data numerically or alphabetically, you can simply use order by [column]. If you want to sort using a custom hierarchy, use a case statement.
Group ----- Total Young MiddleAge Old Male Female
Using a basic order by:
Select * from MyTable Order by Group
returns an alphabetical sort, which isn't always desirable:
Group ----- Female Male MiddleAge Old Total Young
Adding a 'case' statement, assigning ascending numerical values in the order you want your data sorted:
Select * from MyTable Order by case Group
when 'Total' then 10 when 'Male' then 20 when 'Female' then 30 when 'Young' then 40 when 'MiddleAge' then 50 when 'Old' then 60 end
returns data in the order specified:
Group ----- Total Male
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Female Young MiddleAge Old
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Chapter 74: Privileges or Permissions
Section 74.1: Simple rules
Granting permission to create tables
USE AdventureWorks; GRANT CREATE TABLE TO MelanieK; GO
Granting SHOWPLAN permission to an application role
USE AdventureWorks2012; GRANT SHOWPLAN TO AuditMonitor; GO
Granting CREATE VIEW with GRANT OPTION
USE AdventureWorks2012; GRANT CREATE VIEW TO CarmineEs WITH GRANT OPTION; GO
Granting all rights to a user on a specific database
use YourDatabase go exec sp_addrolemember 'db_owner', 'UserName' go
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Chapter 75: SQLCMD
Section 75.1: SQLCMD.exe called from a batch file or command line
echo off
cls
sqlcmd.exe -S "your server name" -U "sql user name" -P "sql password" -d "name of databse" -Q "here you may write your query/stored procedure"
Batch files like these can be used to automate tasks, for example to make backups of databases at a specified time (can be scheduled with Task Scheduler) for a SQL Server Express version where Agent Jobs can't be used.
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Chapter 76: Resource Governor
Section 76.1: Reading the Statistics
select * from sys.dm_resource_governor_workload_groups
select * from sys.dm_resource_governor_resource_pools
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Chapter 77: File Group
Section 77.1: Create filegroup in database
We can create it by two way. First from database properties designer mode:
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And by sql scripts:
USE master; GO -- Create the database with the default data -- filegroup and a log file. Specify the -- growth increment and the max size for the -- primary data file.
CREATE DATABASE TestDB ON PRIMARY (
NAME = 'TestDB_Primary', FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\TestDB_Prm.mdf',
SIZE = 1 GB, MAXSIZE = 10 GB, FILEGROWTH = 1 GB ), FILEGROUP TestDB_FG1 (
NAME = 'TestDB_FG1_1', FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\TestDB_FG1_1.ndf',
SIZE = 10 MB, MAXSIZE = 10 GB, FILEGROWTH = 1 GB ),
(
NAME = 'TestDB_FG1_2', FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\TestDB_FG1_2.ndf',
SIZE = 10 MB, MAXSIZE = 10 GB, FILEGROWTH = 1 GB ) LOG ON (
NAME = 'TestDB_log', FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\TestDB.ldf', SIZE = 10 MB, MAXSIZE = 10 GB, FILEGROWTH = 1 GB );
go ALTER DATABASE TestDB MODIFY FILEGROUP TestDB_FG1 DEFAULT; go
-- Create a table in the user-defined filegroup. USE TestDB; Go
CREATE TABLE MyTable (
col1 INT PRIMARY KEY, col2 CHAR(8) ) ON TestDB_FG1; GO
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Chapter 78: Basic DDL Operations in MS SQL Server
Section 78.1: Getting started
This section describes some basic DDL (="Data Definition Language") commands to create a database, a table within a database, a view and finally a stored procedure.
Create Database
The following SQL command creates a new database Northwind on the current server, using pathC:\Program Files\Microsoft SQL Server\MSSQL11.INSTSQL2012\MSSQL\DATA\:
USE [master] GO
CREATE DATABASE [Northwind]
CONTAINMENT = NONE ON PRIMARY (
NAME = N'Northwind', FILENAME = N'C:\Program Files\Microsoft SQL Server\MSSQL11.INSTSQL2012\MSSQL\DATA\Northwind.mdf' , SIZE = 5120KB , MAXSIZE = UNLIMITED, FILEGROWTH = 1024KB
) LOG ON (
NAME = N'Northwind_log', FILENAME = N'C:\Program Files\Microsoft SQL Server\MSSQL11.INSTSQL2012\MSSQL\DATA\Northwind_log.ldf' , SIZE = 1536KB , MAXSIZE = 2048GB , FILEGROWTH = 10%
) GO
ALTER DATABASE [Northwind] SET COMPATIBILITY_LEVEL = 110 GO
Note: A T-SQL database consists of two files, the database file *.mdf, and its transaction log *.ldf. Both need to be specified when a new database is created.
Create Table
The following SQL command creates a new table Categories in the current database, using schema dbo (you can switch database context with Use <DatabaseName>):
CREATE TABLE dbo.Categories(
CategoryID int IDENTITY NOT NULL, CategoryName nvarchar(15) NOT NULL, Description ntext NULL, Picture image NULL,
CONSTRAINT PK_Categories PRIMARY KEY CLUSTERED (
CategoryID ASC ) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,
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ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON PRIMARY ) ON PRIMARY TEXTIMAGE_ON PRIMARY
Create View
The following SQL command creates a new view Summary_of_Sales_by_Year in the current database, using schema dbo (you can switch database context with Use <DatabaseName>):
CREATE VIEW dbo.Summary_of_Sales_by_Year AS
SELECT ord.ShippedDate, ord.OrderID, ordSub.Subtotal FROM Orders ord INNER JOIN [Order Subtotals] ordSub ON ord.OrderID = ordSub.OrderID
This will join tables Orders and [Order Subtotals] to display the columns ShippedDate, OrderID and Subtotal. Because table [Order Subtotals] has a blank in its name in the Northwind database, it needs to be enclosed in square brackets.
Create Procedure
The following SQL command creates a new stored procedure CustOrdersDetail in the current database, using schema dbo (you can switch database context with Use <DatabaseName>):
CREATE PROCEDURE dbo.MyCustOrdersDetail @OrderID int, @MinQuantity int=0 AS BEGIN
SELECT ProductName,
UnitPrice=ROUND(Od.UnitPrice, 2), Quantity, Discount=CONVERT(int, Discount * 100), ExtendedPrice=ROUND(CONVERT(money, Quantity * (1 - Discount) * Od.UnitPrice), 2) FROM Products P, [Order Details] Od WHERE Od.ProductID = P.ProductID and Od.OrderID = @OrderID and Od.Quantity>=@MinQuantity END
This stored procedure, after it has been created, can be invoked as follows:
exec dbo.MyCustOrdersDetail 10248
which will return all order details with @OrderId=10248 (and quantity >=0 as default). Or you can specify the optional parameter
exec dbo.MyCustOrdersDetail 10248, 10
which will return only orders with a minimum quantity of 10 (or more).
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Chapter 79: Subqueries
Section 79.1: Subqueries
A subquery is a query within another SQL query. A subquery is also called inner query or inner select and the statement containing a subquery is called an outer query or outer select.
Note
Subqueries must be enclosed within parenthesis, 1. An ORDER BY cannot be used in a subquery. 2. The image type such as BLOB, array, text datatypes are not allowed in subqueries. 3.
Subqueries can be used with select, insert, update and delete statement within where, from, select clause along with IN, comparison operators, etc.
We have a table named ITCompanyInNepal on which we will perform queries to show subqueries examples:
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Examples: SubQueries With Select Statement
with In operator and where clause:
SELECT * FROM ITCompanyInNepal WHERE Headquarter IN (SELECT Headquarter
FROM ITCompanyInNepal WHERE Headquarter = 'USA');
with comparison operator and where clause
SELECT * FROM ITCompanyInNepal WHERE NumberOfEmployee < (SELECT AVG(NumberOfEmployee)
FROM ITCompanyInNepal )
with select clause
SELECT CompanyName,
CompanyAddress, Headquarter, (Select SUM(NumberOfEmployee) FROM ITCompanyInNepal
Where Headquarter = 'USA') AS TotalEmployeeHiredByUSAInKathmandu FROM ITCompanyInNepal WHERE CompanyAddress = 'Kathmandu' AND Headquarter = 'USA'
Subqueries with insert statement
We have to insert data from IndianCompany table to ITCompanyInNepal. The table for IndianCompany is shown below:
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INSERT INTO ITCompanyInNepal SELECT * FROM IndianCompany
Subqueries with update statement
Suppose all the companies whose headquarter is USA decided to fire 50 employees from all US based companies of Nepal due to some change in policy of USA companies.
UPDATE ITCompanyInNepal SET NumberOfEmployee = NumberOfEmployee - 50 WHERE Headquarter IN (SELECT Headquarter
FROM ITCompanyInNepal WHERE Headquarter = 'USA')
Subqueries with Delete Statement
Suppose all the companies whose headquarter is Denmark decided to shutdown their companies from Nepal.
DELETE FROM ITCompanyInNepal WHERE Headquarter IN (SELECT Headquarter
FROM ITCompanyInNepal WHERE Headquarter = 'Denmark')
Chapter 80: Pagination
Row Offset and Paging in Various Versions of SQL Server
Section 80.1: Pagination with OFFSET FETCH
Version ≥ SQL Server 2012
The OFFSET FETCH clause implements pagination in a more concise manner. With it, it's possible to skip N1 rows (specified in OFFSET) and return the next N2 rows (specified in FETCH):
SELECT * FROM sys.objects ORDER BY object_id OFFSET 40 ROWS FETCH NEXT 10 ROWS ONLY
The ORDER BY clause is required in order to provide deterministic results.
Section 80.2: Paginaton with inner query
In earlier versions of SQL Server, developers had to use double sorting combined with the TOP keyword to return rows in a page:
SELECT TOP 10 * FROM (
SELECT TOP 50 object_id,
name, type, create_date FROM sys.objects ORDER BY name ASC ) AS data ORDER BY name DESC
The inner query will return the first 50 rows ordered by name. Then the outer query will reverse the order of these 50 rows and select the top 10 rows (these will be last 10 rows in the group before the reversal).
Section 80.3: Paging in Various Versions of SQL Server
SQL Server 2012 / 2014
DECLARE @RowsPerPage INT = 10, @PageNumber INT = 4 SELECT OrderId, ProductId FROM OrderDetail ORDER BY OrderId OFFSET (@PageNumber - 1) * @RowsPerPage ROWS FETCH NEXT @RowsPerPage ROWS ONLY
SQL Server 2005/2008/R2
DECLARE @RowsPerPage INT = 10, @PageNumber INT = 4 SELECT OrderId, ProductId FROM (
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SELECT OrderId, ProductId, ROW_NUMBER() OVER (ORDER BY OrderId) AS RowNum FROM OrderDetail) AS OD WHERE OD.RowNum BETWEEN ((@PageNumber - 1 ) * @RowsPerPage) + 1 AND @RowsPerPage * @PageNumber
SQL Server 2000
DECLARE @RowsPerPage INT = 10, @PageNumber INT = 4 SELECT OrderId, ProductId FROM (SELECT TOP (@RowsPerPage) OrderId, ProductId
FROM (SELECT TOP ((@PageNumber)*@RowsPerPage) OrderId, ProductId
FROM OrderDetail ORDER BY OrderId) AS OD ORDER BY OrderId DESC) AS OD2 ORDER BY OrderId ASC
Section 80.4: SQL Server 2012/2014 using ORDER BY OFFSET and FETCH NEXT
For getting the next 10 rows just run this query:
SELECT * FROM TableName ORDER BY id OFFSET 10 ROWS FETCH NEXT 10 ROWS ONLY;
Key points to consider when using it:
ORDER BY is mandatory to use OFFSET and FETCH clause. OFFSET clause is mandatory with FETCH. You can never use, ORDER BY ... FETCH. TOP cannot be combined with OFFSET and FETCH in the same query expression.
Section 80.5: Pagination using ROW_NUMBER with a Common Table Expression
Version ≥ SQL Server 2008
The ROW_NUMBER function can assign an incrementing number to each row in a result set. Combined with a Common Table Expression that uses a BETWEEN operator, it is possible to create 'pages' of result sets. For example: page one containing results 1-10, page two containing results 11-20, page three containing results 21-30, and so on.
WITH data AS (
SELECT ROW_NUMBER() OVER (ORDER BY name) AS row_id,
object_id, name, type, create_date FROM sys.objects ) SELECT * FROM data WHERE row_id BETWEEN 41 AND 50
Note: It is not possible to use ROW_NUMBER in a WHERE clause like:
SELECT object_id,
name, type,
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create_date FROM sys.objects WHERE ROW_NUMBER() OVER (ORDER BY name) BETWEEN 41 AND 50
Although this would be more convenient, SQL server will return the following error in this case:
Msg 4108, Level 15, State 1, Line 6
Windowed functions can only appear in the SELECT or ORDER BY clauses.
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Chapter 81: CLUSTERED COLUMNSTORE
Section 81.1: Adding clustered columnstore index on existing table
CREATE CLUSTERED COLUMNSTORE INDEX enables you to organize a table in column format:
DROP TABLE IF EXISTS Product GO CREATE TABLE Product (
Name nvarchar(50) NOT NULL, Color nvarchar(15), Size nvarchar(5) NULL, Price money NOT NULL, Quantity int ) GO CREATE CLUSTERED COLUMNSTORE INDEX cci ON Product
Section 81.2: Rebuild CLUSTERED COLUMNSTORE index
Clustered column store index can be rebuilt if you have a lot of deleted rows:
ALTER INDEX cci ON Products REBUILD PARTITION = ALL
Rebuilding CLUSTERED COLUMNSTORE will "reload" data from the current table into new one and apply compression again, remove deleted rows, etc.
You can rebuild one or more partitions.
Section 81.3: Table with CLUSTERED COLUMNSTORE index
If you want to have a table organized in column-store format instead of row store, add INDEX cci CLUSTERED COLUMNSTORE in definition of table:
DROP TABLE IF EXISTS Product GO CREATE TABLE Product ( ProductID int, Name nvarchar(50) NOT NULL, Color nvarchar(15), Size nvarchar(5) NULL, Price money NOT NULL, Quantity int, INDEX cci CLUSTERED COLUMNSTORE )
COLUMNSTORE tables are better for tables where you expect full scans and reports, while row store tables are better for tables where you will read or update smaller sets of rows.
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Chapter 82: Parsename
'object_name' object_piece Is the name of the object for which to retrieve the specified object part. object_name is sysname. This parameter is an optionally-qualified object name. If all parts of the object name are qualified, this name can have four parts: the server name, the database name, the owner name, and the object name.
Is the object part to return. object_piece is of type int, and can have these values:1 = Object name 2 = Schema name 3 = Database name 4 = Server name
Section 82.1: PARSENAME
Declare @ObjectName nVarChar(1000) Set @ObjectName = 'HeadOfficeSQL1.Northwind.dbo.Authors'
SELECT
PARSENAME(@ObjectName, 4) as Server ,PARSENAME(@ObjectName, 3) as DB ,PARSENAME(@ObjectName, 2) as Owner ,PARSENAME(@ObjectName, 1) as Object
Returns:
Server DB HeadofficeSQL1 Northwind
Owner Object dbo Authors
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Chapter 83: Installing SQL Server on Windows
Section 83.1: Introduction
These are the available editions of SQL Server, as told by the Editions Matrix:
Express: Entry-level free database. Includes core-RDBMS functionality. Limited to 10G of disk size. Ideal for development and testing. Standard Edition: Standard Licensed edition. Includes core functionality and Business Intelligence capabilities. Enterprise Edition: Full-featured SQL Server edition. Includes advanced security and data warehousing capabilities. Developer Edition: Includes all of the features from Enterprise Edition and no limitations, and it is free to download and use for development purposes only.
After downloading/acquiring SQL Server, the installation gets executed with SQLSetup.exe, which is available as a GUI or a command-line program.
Installing via either of these will require you to specify a product key and run some initial configuration that includes enabling features, separate services and setting the initial parameters for each of them. Additional services and features can be enabled at any time by running the SQLSetup.exe program in either the command-line or the GUI version.
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Chapter 84: Analyzing a Query
Section 84.1: Scan vs Seek
When viewing an execution plan, you may see that SQL Server decided to do a Seek or a Scan.
A Seek occurs when SQL Server knows where it needs to go and only grab specific items. This typically occurs when good filters on put in a query, such as where name = 'Foo'.
A Scan is when SQL Server doesn't know exactly where all of the data it needs is, or decided that the Scan would be more efficient than a Seek if enough of the data is selected.
Seeks are typically faster since they are only grabbing a sub-section of the data, whereas Scans are selecting a majority of the data.
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Chapter 85: Query Hints
Section 85.1: JOIN Hints
When you join two tables, SQL Server query optimizer (QO) can choose different types of joins that will be used in query:
HASH join LOOP join MERGE join
QO will explore plans and choose the optimal operator for joining tables. However, if you are sure that you know what would be the optimal join operator, you can specify what kind of JOIN should be used. Inner LOOP join will force QO to choose Nested loop join while joining two tables:
select top 100 * from Sales.Orders o
inner loop join Sales.OrderLines ol on o.OrderID = ol.OrderID
inner merge join will force MERGE join operator:
select top 100 * from Sales.Orders o
inner merge join Sales.OrderLines ol on o.OrderID = ol.OrderID
inner hash join will force HASH join operator:
select top 100 * from Sales.Orders o
inner hash join Sales.OrderLines ol on o.OrderID = ol.OrderID
Section 85.2: GROUP BY Hints
When you use GROUP BY clause, SQL Server query optimizer (QO) can choose different types of grouping operators:
HASH Aggregate that creates hash-map for grouping entries Stream Aggregate that works well with pre-ordered inputs
You can explicitly require that QO picks one or another aggregate operator if you know what would be the optimal. With OPTION (ORDER GROUP), QO will always choose Stream aggregate and add Sort operator in front of Stream aggregate if input is not sorted:
select OrderID, AVG(Quantity) from Sales.OrderLines group by OrderID OPTION (ORDER GROUP)
With OPTION (HASH GROUP), QO will always choose Hash aggregate :
select OrderID, AVG(Quantity)
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from Sales.OrderLines group by OrderID OPTION (HASH GROUP)
Section 85.3: FAST rows hint
Specifies that the query is optimized for fast retrieval of the first number_rows. This is a nonnegative integer. After the first number_rows are returned, the query continues execution and produces its full result set.
select OrderID, AVG(Quantity) from Sales.OrderLines group by OrderID OPTION (FAST 20)
Section 85.4: UNION hints
When you use UNION operator on two query results, Query optimizer (QO) can use following operators to create a union of two result sets:
Merge (Union) Concat (Union) Hash Match (Union)
You can explicitly specify what operator should be used using OPTION() hint:
select OrderID, OrderDate, ExpectedDeliveryDate, Comments from Sales.Orders where OrderDate > DATEADD(day, -1, getdate()) UNION select PurchaseOrderID as OrderID, OrderDate, ExpectedDeliveryDate, Comments from Purchasing.PurchaseOrders where OrderDate > DATEADD(day, -1, getdate()) OPTION(HASH UNION) -- or OPTION(CONCAT UNION) -- or OPTION(MERGE UNION)
Section 85.5: MAXDOP Option
Specifies the max degree of parallelism for the query specifying this option.
SELECT OrderID,
AVG(Quantity) FROM Sales.OrderLines GROUP BY OrderID OPTION (MAXDOP 2);
This option overrides the MAXDOP configuration option of sp_configure and Resource Governor. If MAXDOP is set to zero then the server chooses the max degree of parallelism.
Section 85.6: INDEX Hints
Index hints are used to force a query to use a specific index, instead of allowing SQL Server's Query Optimizer to choose what it deems the best index. In some cases you may gain benefits by specifying the index a query must use. Usually SQL Server's Query Optimizer chooses the best index suited for the query, but due to missing/outdated statistics or specific needs you can force it.
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SELECT * FROM mytable WITH (INDEX (ix_date)) WHERE field1 > 0
AND CreationDate > '20170101'
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Chapter 86: Query Store
Section 86.1: Enable query store on database
Query store can be enabled on database by using the following command:
ALTER DATABASE tpch SET QUERY_STORE = ON
SQL Server/Azure SQL Database will collect information about executed queries and provide information in sys.query_store views:
sys.query_store_query sys.query_store_query_text sys.query_store_plan sys.query_store_runtime_stats sys.query_store_runtime_stats_interval sys.database_query_store_options sys.query_context_settings
Section 86.2: Get execution statistics for SQL queries/plans
The following query will return informationa about qeries, their plans and average statistics regarding their duration, CPU time, physical and logical io reads.
SELECT Txt.query_text_id, Txt.query_sql_text, Pl.plan_id,
avg_duration, avg_cpu_time, avg_physical_io_reads, avg_logical_io_reads FROM sys.query_store_plan AS Pl JOIN sys.query_store_query AS Qry ON Pl.query_id = Qry.query_id JOIN sys.query_store_query_text AS Txt
ON Qry.query_text_id = Txt.query_text_id JOIN sys.query_store_runtime_stats Stats
ON Pl.plan_id = Stats.plan_id
Section 86.3: Remove data from query store
If you want to remove some query or query plan from query store, you can use the following commands:
EXEC sp_query_store_remove_query 4; EXEC sp_query_store_remove_plan 3;
Parameters for these stored procedures are query/plan id retrieved from system views.
You can also just remove execution statistics for particular plan without removing the plan from the store:
EXEC sp_query_store_reset_exec_stats 3;
Parameter provided to this procedure plan id.
Section 86.4: Forcing plan for query
SQL Query optimizer will choose the baes possible plan that he can find for some query. If you can find some plan
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that works optimally for some query, you can force QO to always use that plan using the following stored procedure:
EXEC sp_query_store_unforce_plan @query_id, @plan_id
From this point, QO will always use plan provided for the query.
If you want to remove this binding, you can use the following stored procedure:
EXEC sp_query_store_force_plan @query_id, @plan_id
From this point, QO will again try to find the best plan.
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Chapter 87: Querying results by page
Section 87.1: Row_Number()
SELECT Row_Number() OVER(ORDER BY UserName) As RowID, UserFirstName, UserLastName FROM Users
From which it will yield a result set with a RowID field which you can use to page between.
SELECT * FROM
( SELECT Row_Number() OVER(ORDER BY UserName) As RowID, UserFirstName, UserLastName
FROM Users ) As RowResults WHERE RowID Between 5 AND 10
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Chapter 88: Schemas
Section 88.1: Purpose
Schema refers to a specific database tables and how they are related to each other. It provides an organisational blueprint of how the database is constructed. Additional benefits of implementing database schemas is that schemas can be used as a method restricting / granting access to specific tables within a database.
Section 88.2: Creating a Schema
CREATE SCHEMA dvr AUTHORIZATION Owner
CREATE TABLE sat_Sales (source int, cost int, partid int) GRANT SELECT ON SCHEMA :: dvr TO User1 DENY SELECT ON SCHEMA :: dvr to User 2 GO
Section 88.3: Alter Schema
ALTER SCHEMA dvr
TRANSFER dbo.tbl_Staging; GO
This would transfer the tbl_Staging table from the dbo schema to the dvr schema
Section 88.4: Dropping Schemas
DROP SCHEMA dvr
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Chapter 89: Backup and Restore Database
Parameter Details database The name of the database to backup or restore
backup_device
The device to commas ( , )
backup or restore the database from, Like {DISK or TAPE}. Can be separated by
with_options
Various options which can be used while performing the operation. Like formatting the disk where the backup is to be placed or restoring the database with replace option.
Section 89.1: Basic Backup to disk with no options
The following command backs up the 'Users' database to 'D:\DB_Backup' file. Its better to not give an extension.
BACKUP DATABASE Users TO DISK = 'D:\DB_Backup'
Section 89.2: Basic Restore from disk with no options
The following command restores the 'Users' database from 'D:\DB_Backup' file.
RESTORE DATABASE Users FROM DISK = 'D:\DB_Backup'
Section 89.3: RESTORE Database with REPLACE
When you try to restore database from another server you might get the following error:
Error 3154: The backup set holds a backup of a database other than the existing database.
In that case you should use WITH REPLACE option to replace database with the database from backup:
RESTORE DATABASE WWIDW FROM DISK = 'C:\Backup\WideWorldImportersDW-Full.bak' WITH REPLACE
Even in this case you might get the errors saying that files cannot be located on some path:
Msg 3156, Level 16, State 3, Line 1 File 'WWI_Primary' cannot be restored to 'D:\Data\WideWorldImportersDW.mdf'. Use WITH MOVE to identify a valid location for the file.
This error happens probably because your files were not placed on the same folder path that exist on new server. In that case you should move individual database files to new location:
RESTORE DATABASE WWIDW FROM DISK = 'C:\Backup\WideWorldImportersDW-Full.bak' WITH REPLACE, MOVE 'WWI_Primary' to 'C:\Data\WideWorldImportersDW.mdf', MOVE 'WWI_UserData' to 'C:\Data\WideWorldImportersDW_UserData.ndf', MOVE 'WWI_Log' to 'C:\Data\WideWorldImportersDW.ldf', MOVE 'WWIDW_InMemory_Data_1' to 'C:\Data\WideWorldImportersDW_InMemory_Data_1'
With this statement you can replace database with all database files moved to new location.
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Chapter 90: Transaction handling
Parameter Details
transaction_name
for naming your transaction - useful with the parameter [with mark] which will allow a meaningfull logging -- case-sensitive (!)
with mark ['description'] can be added to [transaction_name] and will store a mark in the log
Section 90.1: basic transaction skeleton with error handling
BEGIN TRY -- start error handling
BEGIN TRANSACTION; -- from here on transactions (modifictions) are not final
-- start your statement(s) select 42/0 as ANSWER -- simple SQL Query with an error -- end your statement(s) COMMIT TRANSACTION; -- finalize all transactions (modifications) END TRY -- end error handling -- jump to end BEGIN CATCH -- execute this IF an error occurred
ROLLBACK TRANSACTION; -- undo any transactions (modifications) -- put together some information as a query
SELECT
ERROR_NUMBER() AS ErrorNumber ,ERROR_SEVERITY() AS ErrorSeverity ,ERROR_STATE() AS ErrorState ,ERROR_PROCEDURE() AS ErrorProcedure ,ERROR_LINE() AS ErrorLine ,ERROR_MESSAGE() AS ErrorMessage;
END CATCH; -- final line of error handling GO -- execute previous code
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Chapter 91: Natively compiled modules (Hekaton)
Section 91.1: Natively compiled stored procedure
In a procedure with native compilation, T-SQL code is compiled to dll and executed as native C code. To create a Native Compiled stored Procedure you need to:
Use standard CREATE PROCEDURE syntax Set NATIVE_COMPILATION option in stored procedure definition Use SCHEMABINDING option in stored procedure definition Define EXECUTE AS OWNER option in stored procedure definition
Instead of standard BEGIN END block, you need to use BEGIN ATOMIC block:
BEGIN ATOMIC
WITH (TRANSACTION ISOLATION LEVEL=SNAPSHOT, LANGUAGE='us_english') -- T-Sql code goes here END
Example:
CREATE PROCEDURE usp_LoadMemOptTable (@maxRows INT, @FullName NVARCHAR(200)) WITH
NATIVE_COMPILATION, SCHEMABINDING, EXECUTE AS OWNER AS BEGIN ATOMIC WITH (TRANSACTION ISOLATION LEVEL=SNAPSHOT, LANGUAGE='us_english')
DECLARE @i INT = 1 WHILE @i <= @maxRows BEGIN
INSERT INTO dbo.MemOptTable3 VALUES(@i, @FullName, GETDATE()) SET @i = @i+1 END END GO
Section 91.2: Natively compiled scalar function
Code in natively compiled function will be transformed into C code and compiled as dll. To create a Native Compiled scalar function you need to:
Use standard CREATE FUNCTION syntax Set NATIVE_COMPILATION option in function definition Use SCHEMABINDING option in function definition
Instead of standard BEGIN END block, you need to use BEGIN ATOMIC block:
BEGIN ATOMIC
WITH (TRANSACTION ISOLATION LEVEL=SNAPSHOT, LANGUAGE='us_english') -- T-Sql code goes here END
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Example:
CREATE FUNCTION [dbo].[udfMultiply]( @v1 int, @v2 int ) RETURNS bigint WITH NATIVE_COMPILATION, SCHEMABINDING AS BEGIN ATOMIC WITH (TRANSACTION ISOLATION LEVEL = SNAPSHOT, LANGUAGE = N'English')
DECLARE @ReturnValue bigint; SET @ReturnValue = @v1 * @v2;
RETURN (@ReturnValue); END
-- usage sample: SELECT dbo.udfMultiply(10, 12)
Section 91.3: Native inline table value function
Native compiled table value function returns table as result. Code in natively compiled function will be transformed into C code and compiled as dll. Only inline table valued functions are supported in version 2016. To create a native table value function you need to:
Use standard CREATE FUNCTION syntax Set NATIVE_COMPILATION option in function definition Use SCHEMABINDING option in function definition
Instead of standard BEGIN END block, you need to use BEGIN ATOMIC block:
BEGIN ATOMIC
WITH (TRANSACTION ISOLATION LEVEL=SNAPSHOT, LANGUAGE='us_english') -- T-Sql code goes here END
Example:
CREATE FUNCTION [dbo].[udft_NativeGetBusinessDoc] (
@RunDate VARCHAR(25) ) RETURNS TABLE WITH SCHEMABINDING,
NATIVE_COMPILATION AS
RETURN (
SELECT BusinessDocNo,
ProductCode, UnitID, ReasonID, PriceID, RunDate, ReturnPercent, Qty, RewardAmount, ModifyDate, UserID FROM dbo.[BusinessDocDetail_11] WHERE RunDate >= @RunDate
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);
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Chapter 92: Spatial Data
There are 2 spatial data types
Geometry X/Y coordinate system for a flat surface
Geography Latitude/Longitude coordinate system for a curved surface (the earth). There are multiple projections of curved surfaces so each geography spatial must let SQL Server know which projection to use. The usual Spatial Reference ID (SRID) is 4326, which is measuring distances in Kilometers. This is the default SRID used in most web maps
Section 92.1: POINT
Creates a single Point. This will be a geometry or geography point depending on the class used.
Parameter Detail Lat or X Is a float expression representing the x-coordinate of the Point being generated
Long or Y Is a float expression representing the y-coordinate of the Point being generated String Well Known Text (WKB) of a geometry/geography shape
Binary Well Known Binary (WKB) of a geometry/geography shape
SRID
Is an int expression representing the spatial reference ID (SRID) of the geometry/geography instance you wish to return
--Explicit constructor DECLARE @gm1 GEOMETRY = GEOMETRY::Point(10,5,0)
DECLARE @gg1 GEOGRAPHY = GEOGRAPHY::Point(51.511601,-0.096600,4326)
--Implicit constructor (using WKT - Well Known Text) DECLARE @gm1 GEOMETRY = GEOMETRY::STGeomFromText('POINT(5 10)', 0)
DECLARE @gg1 GEOGRAPHY= GEOGRAPHY::STGeomFromText('POINT(-0.096600 51.511601)', 4326)
--Implicit constructor (using WKB - Well Known Binary) DECLARE @gm1 GEOMETRY = GEOMETRY::STGeomFromWKB(0x010100000000000000000014400000000000002440, 0)
DECLARE @gg1 GEOGRAPHY= GEOGRAPHY::STGeomFromWKB(0x01010000005F29CB10C7BAB8BFEACC3D247CC14940, 4326)
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Chapter 93: Dynamic SQL
Section 93.1: Execute SQL statement provided as string
In some cases, you would need to execute SQL query placed in string. EXEC, EXECUTE, or system procedure sp_executesql can execute any SQL query provided as string:
sp_executesql N'SELECT * FROM sys.objects' -- or sp_executesql @stmt = N'SELECT * FROM sys.objects' -- or EXEC sp_executesql N'SELECT * FROM sys.objects' -- or EXEC('SELECT * FROM sys.columns') -- or EXECUTE('SELECT * FROM sys.tables')
This procedure will return the same result-set as SQL query provided as statement text. sp_executesql can execute SQL query provided as string literal, variable/parameter, or even expression:
declare @table nvarchar(40) = N'product items' EXEC(N'SELECT * FROM ' + @table) declare @sql nvarchar(40) = N'SELECT * FROM ' + QUOTENAME(@table); EXEC sp_executesql @sql
You need QUOTENAME function to escape special characters in @table variable. Without this function you would get syntax error if @table variable contains something like spaces, brackets, or any other special character.
Section 93.2: Dynamic SQL executed as dierent user
You can execute SQL query as different user using AS USER = 'name of database user'
EXEC(N'SELECT * FROM product') AS USER = 'dbo'
SQL query will be executed under dbo database user. All permission checks applicable to dbo user will be checked on SQL query.
Section 93.3: SQL Injection with dynamic SQL
Dynamic queries are
SET @sql = N'SELECT COUNT(*) FROM AppUsers WHERE Username = ''' + @user + ''' AND Password = ''' + @pass + '''' EXEC(@sql)
If value of user variable is myusername'' OR 1=1 -- the following query will be executed:
SELECT COUNT(*) FROM AppUsers WHERE Username = 'myusername' OR 1=1 --' AND Password = ''
Comment at the end of value of variable @username will comment-out trailing part of the query and condition 1=1 will be evaluated. Application that checks it there at least one user returned by this query will return count greater than 0 and login will succeed.
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Using this approach attacker can login into application even if he don't know valid username and password.
Section 93.4: Dynamic SQL with parameters
In order to avoid injection and escaping problems, dynamic SQL queries should be executed with parameters, e.g.:
SET @sql = N'SELECT COUNT(*) FROM AppUsers WHERE Username = @user AND Password = @pass EXEC sp_executesql @sql, '@user nvarchar(50), @pass nvarchar(50)', @username, @password
Second parameter is a list of parameters used in query with their types, after this list are provided variables that will be used as parameter values.
sp_executesql will escape special characters and execute sql query.
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Chapter 94: Dynamic data masking
Section 94.1: Adding default mask on the column
If you add default mask on the column, instead of actual value in SELECT statement will be shown mask:
ALTER TABLE Company ALTER COLUMN Postcode ADD MASKED WITH (FUNCTION = 'default()')
Section 94.2: Mask email address using Dynamic data masking
If you have email column you can mask it with email() mask:
ALTER TABLE Company ALTER COLUMN Email ADD MASKED WITH (FUNCTION = 'email()')
When user tries to select emails from Company table, he will get something like the following values:
mXXX@XXXX.com
zXXX@XXXX.com
rXXX@XXXX.com
Section 94.3: Add partial mask on column
You can add partial mask on the column that will show few characters from te beginning and the end of the string and show mask instead of the characters in the middle:
ALTER TABLE Company ALTER COLUMN Phone ADD MASKED WITH (FUNCTION = 'partial(5,"XXXXXXX",2)')
In the parameters of the partial function you can specify how many values from the beginning will be shown, how many values from the end will be shown, and what woudl be the pattern that is shown in the middle.
When user tries to select emails from Company table, he will get something like the following values:
(381)XXXXXXX39
(360)XXXXXXX01
(415)XXXXXXX05
Section 94.4: Showing random value from the range using random() mask
Random mask will show a rundom number from the specified range instead of the actual value:
ALTER TABLE Product ALTER COLUMN Price ADD MASKED WITH (FUNCTION = 'random(100,200)')
Note that is some cases displayed value might match actual value in column (if randomly selected number matches
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value in the cell).
Section 94.5: Controlling who can see unmasked data
You can grant in-privileged users right to see unmasked values using the following statement:
GRANT UNMASK TO MyUser
If some user already has unmask permission, you can revoke this permission:
REVOKE UNMASK TO MyUser
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Chapter 95: Export data in txt file by using SQLCMD
Section 95.1: By using SQLCMD on Command Prompt
Command Structure is
sqlcmd -S yourservername\instancename -d database_name -o outputfilename_withpath -Q "your select query"
Switches are as follows
-S
for servername and instance name
-d
for source database
-o
for target outputfile (it will create output file)
-Q
for query to fetch data
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Chapter 96: Common Language Runtime Integration
Section 96.1: Enable CLR on database
CLR procedures are not enabled by default. You need to run the following queries to enable CLR:
sp_configure 'show advanced options', 1; GO RECONFIGURE; GO sp_configure 'clr enabled', 1; GO RECONFIGURE; GO
In addition, if some CLR module need external access, you should set TRUSTWORTHY property to ON in your database:
ALTER DATABASE MyDbWithClr SET TRUSTWORTHY ON
Section 96.2: Adding .dll that contains Sql CLR modules
Procedures, functions, triggers, and types written in .Net languages are stored in .dll files. Once you create .dll file containing CLR procedures you should import it into SQL Server:
CREATE ASSEMBLY MyLibrary FROM 'C:\lib\MyStoredProcedures.dll'
WITH PERMISSION_SET = EXTERNAL_ACCESS
PERMISSION_SET is Safe by default meaning that code in .dll don't need permission to access external resources (e.g. files, web sites, other servers), and that it will not use native code that can access memory.
PERMISSION_SET = EXTERNAL_ACCESS is used to mark assemblies that contain code that will access external resources.
you can find information about current CLR assembly files in sys.assemblies view:
SELECT * FROM sys.assemblies asms WHERE is_user_defined = 1
Section 96.3: Create CLR Function in SQL Server
If you have created .Net function, compiled it into .dll, and imported it into SQL server as an assembly, you can create user-defined function that references function in that assembly:
CREATE FUNCTION dbo.TextCompress(@input nvarchar(max)) RETURNS varbinary(max) AS EXTERNAL NAME MyLibrary.[Name.Space.ClassName].TextCompress
You need to specify name of the function and signature with input parameters and return values that match .Net function. In AS EXTERNAL NAME clause you need to specify assembly name, namespace/class name where this
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function is placed and name of the method in the class that contains the code that will be exposed as function.
You can find information about the CLR functions using the following query:
SELECT * FROM dbo.sysobjects WHERE TYPE ='FS'
Section 96.4: Create CLR User-defined type in SQL Server
If you have create .Net class that represents some user-defined type, compiled it into .dll, and imported it into SQL server as an assembly, you can create user-defined function that references this class:
CREATE TYPE dbo.Point EXTERNAL NAME MyLibrary.[Name.Space.Point]
You need to specify name of the type that will be used in T-SQL queries. In EXTERNAL NAME clause you need to specify assembly name, namespace, and class name.
Section 96.5: Create CLR procedure in SQL Server
If you have created .Net method in some class, compiled it into .dll, and imported it into SQL server as an assembly, you can create user-defined stored procedure that references method in that assembly:
CREATE PROCEDURE dbo.DoSomethng(@input nvarchar(max)) AS EXTERNAL NAME MyLibrary.[Name.Space.ClassName].DoSomething
You need to specify name of the procedure and signature with input parameters that match .Net method. In AS EXTERNAL NAME clause you need to specify assembly name, namespace/class name where this procedure is placed and name of the method in the class that contains the code that will be exposed as procedure.
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Chapter 97: Delimiting special characters and reserved words
Section 97.1: Basic Method
The basic method to escape reserved words for SQL Server is the use of the square brackets ([ and ]). For example, Description and Name are reserved words; however, if there is an object using both as names, the syntax used is:
SELECT [Description] FROM dbo.TableName WHERE [Name] = 'foo'
The only special character for SQL Server is the single quote ' and it is escaped by doubling its usage. For example, to find the name O'Shea in the same table, the following syntax would be used:
SELECT [Description] FROM dbo.TableName WHERE [Name] = 'O''Shea'
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Chapter 98: DBCC
Section 98.1: DBCC statement
DBCC statements act as Database Console Commands for SQL Server. To get the syntax information for the specified DBCC command use DBCC HELP (...) statement.
The following example returns all DBCC statements for which Help is available:
DBCC HELP ('?');
The following example returns options for DBCC CHECKDB statement:
DBCC HELP ('CHECKDB');
Section 98.2: DBCC maintenance commands
DBCC commands enable user to maintain space in database, clean caches, shrink databases and tables.
Examples are:
DBCC DROPCLEANBUFFERS
Removes all clean buffers from the buffer pool, and columnstore objects from the columnstore object pool.
DBCC FREEPROCCACHE -- or DBCC FREEPROCCACHE (0x060006001ECA270EC0215D05000000000000000000000000);
Removes all SQL query in plan cache. Every new plan will be recompiled: You can specify plan handle, query handle to clean plans for the specific query plan or SQL statement.
DBCC FREESYSTEMCACHE ('ALL', myresourcepool); -- or DBCC FREESYSTEMCACHE;
Cleans all cached entries created by system. It can clean entries o=in all or some specified resource pool (myresourcepool in the example above)
DBCC FLUSHAUTHCACHE
Empties the database authentication cache containing information about logins and firewall rules.
DBCC SHRINKDATABASE (MyDB [, 10]);
Shrinks database MyDB to 10%. Second parameter is optional. You can use database id instead of name.
DBCC SHRINKFILE (DataFile1, 7);
Shrinks data file named DataFile1 in the current database. Target size is 7 MB (tis parameter is optional).
DBCC CLEANTABLE (AdventureWorks2012,'Production.Document', 0)
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Reclaims a space from specified table
Section 98.3: DBCC validation statements
DBCC commands enable user to validate state of database.
ALTER TABLE Table1 WITH NOCHECK ADD CONSTRAINT chkTab1 CHECK (Col1 > 100); GO DBCC CHECKCONSTRAINTS(Table1); --OR DBCC CHECKCONSTRAINTS ('Table1.chkTable1');
Check constraint is added with nocheck options, so it will not be checked on existing data. DBCC will trigger constraint check.
Following DBCC commands check integrity of database, table or catalog:
DBCC CHECKTABLE tablename1 | tableid DBCC CHECKDB databasename1 | dbid DBCC CHECKFILEGROUP filegroup_name | filegroup_id | 0 DBCC CHECKCATALOG databasename1 | database_id1 | 0
Section 98.4: DBCC informational statements
DBCC commands can show information about database objects.
DBCC PROCCACHE
Displays information in a table format about the procedure cache.
DBCC OUTPUTBUFFER ( session_id [ , request_id ])
Returns the current output buffer in hexadecimal and ASCII format for the specified session_id (and optional request_id).
DBCC INPUTBUFFER ( session_id [ , request_id ])
Displays the last statement sent from a client to an instance of Microsoft SQL Server.
DBCC SHOW_STATISTICS ( table_or_indexed_view_name , column_statistic_or_index_name)
Section 98.5: DBCC Trace commands
Trace flags in SQL Server are used to modify behavior of SQL server, turn on/off some features. DBCC commands can control trace flags:
The following example switches on trace flag 3205 globally and 3206 for the current session:
DBCC TRACEON (3205, -1); DBCC TRACEON (3206);
The following example switches off trace flag 3205 globally and 3206 for the current session:
DBCC TRACEON (3205, -1);
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DBCC TRACEON (3206);
The following example displays the status of trace flags 2528 and 3205:
DBCC TRACESTATUS (2528, 3205);
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Chapter 99: BULK Import
Section 99.1: BULK INSERT
BULK INSERT command can be used to import file into SQL Server:
BULK INSERT People FROM 'f:\orders\people.csv'
BULK INSERT command will map columns in files with columns in target table.
Section 99.2: BULK INSERT with options
You can customize parsing rules using different options in WITH clause:
BULK INSERT People FROM 'f:\orders\people.csv' WITH ( CODEPAGE = '65001',
FIELDTERMINATOR =',', ROWTERMINATOR ='\n' );
In this example, CODEPAGE specifies that a source file in UTF-8 file, and TERMINATORS are coma and new line.
Section 99.3: Reading entire content of file using OPENROWSET(BULK)
You can read content of file using OPENROWSET(BULK) function and store content in some table:
INSERT INTO myTable(content)
SELECT BulkColumn
FROM OPENROWSET(BULK N'C:\Text1.txt', SINGLE_BLOB) AS Document;
SINGLE_BLOB option will read entire content from a file as single cell.
Section 99.4: Read file using OPENROWSET(BULK) and format file
Yu can define format of the file that will be imported using FORMATFILE option:
INSERT INTO mytable SELECT a.* FROM OPENROWSET(BULK 'c:\test\values.txt',
FORMATFILE = 'c:\test\values.fmt') AS a;
The format file, format_file.fmt, describes the columns in values.txt:
9.0 2 1 SQLCHAR 0 10 "\t" 1 ID SQL_Latin1_General_Cp437_BIN 2 SQLCHAR 0 40 "\r\n" 2 Description SQL_Latin1_General_Cp437_BIN
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Section 99.5: Read json file using OPENROWSET(BULK)
You can use OPENROWSET to read content of file and pass it to some other function that will parse results.
The following example shows hot to read entire content of JSON file using OPENROWSET(BULK) and then provide BulkColumn to OPENJSON function that will parse JSON and return columns:
SELECT book.*
FROM OPENROWSET (BULK 'C:\JSON\Books\books.json', SINGLE_CLOB) as j CROSS APPLY OPENJSON(BulkColumn)
WITH( id nvarchar(100), name nvarchar(100), price float,
pages int, author nvarchar(100)) AS book
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Chapter 100: Service broker
Section 100.1: Basics
Service broker is technology based on asyncronous communication between two(or more) entities. Service broker consists of: message types, contracts, queues, services, routes, and at least instance endpoints
More: https://msdn.microsoft.com/en-us/library/bb522893.aspx
Section 100.2: Enable service broker on database
ALTER DATABASE [MyDatabase] SET ENABLE_BROKER WITH ROLLBACK IMMEDIATE;
Section 100.3: Create basic service broker construction on database (single database communication)
USE [MyDatabase]
CREATE MESSAGE TYPE [//initiator] VALIDATION = WELL_FORMED_XML;
GO
CREATE CONTRACT [//call/contract] (
[//initiator] SENT BY INITIATOR ) GO
CREATE QUEUE InitiatorQueue; GO
CREATE QUEUE TargetQueue; GO
CREATE SERVICE InitiatorService
ON QUEUE InitiatorQueue (
[//call/contract]
)
CREATE SERVICE TargetService ON QUEUE TargetQueue (
[//call/contract]
)
GRANT SEND ON SERVICE::[InitiatorService] TO PUBLIC GO
GRANT SEND ON SERVICE::[TargetService] TO PUBLIC GO
We don't need route for one database communication.
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Section 100.4: How to send basic communication through service broker
For this demonstration we will use service broker construction created in another part of this documentation. Mentioned part is named 3. Create basic service broker construction on database (single database communication).
USE [MyDatabase]
DECLARE @ch uniqueidentifier = NEWID() DECLARE @msg XML
BEGIN DIALOG CONVERSATION @ch
FROM SERVICE [InitiatorService] TO SERVICE 'TargetService' ON CONTRACT [//call/contract] WITH ENCRYPTION = OFF; -- more possible options
SET @msg = (
SELECT 'HelloThere' "elementNum1" FOR XML PATH(''), ROOT('ExampleRoot'), ELEMENTS XSINIL, TYPE );
SEND ON CONVERSATION @ch MESSAGE TYPE [//initiator] (@msg); END CONVERSATION @ch;
After this conversation will be your msg in TargetQueue
Section 100.5: How to receive conversation from TargetQueue automatically
For this demonstration we will use service broker construction created in another part of this documentation. Mentioned part is called 3. Create basic service broker construction on database (single database communication).
First we need to create a procedure that is able to read and process data from the Queue
USE [MyDatabase] GO
SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO
CREATE PROCEDURE [dbo].[p_RecieveMessageFromTargetQueue]
AS BEGIN
declare @message_body xml, @message_type_name nvarchar(256), @conversation_handle uniqueidentifier, @messagetypename nvarchar(256);
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WHILE 1=1 BEGIN
BEGIN TRANSACTION
WAITFOR( RECEIVE TOP(1) @message_body = CAST(message_body as xml), @message_type_name = message_type_name, @conversation_handle = conversation_handle, @messagetypename = message_type_name FROM DwhInsertSmsQueue ), TIMEOUT 1000;
IF (@@ROWCOUNT = 0)
BEGIN
ROLLBACK TRANSACTION BREAK END
IF (@messagetypename = '//initiator')
BEGIN
IF OBJECT_ID('MyDatabase..MyExampleTableHelloThere') IS NOT NULL
DROP TABLE dbo.MyExampleTableHelloThere
SELECT @message_body.value('(/ExampleRoot/"elementNum1")[1]', 'VARCHAR(50)') AS MyExampleMessage
INTO dbo.MyExampleTableHelloThere
END
IF (@messagetypename = 'http://schemas.microsoft.com/SQL/ServiceBroker/EndDialog')
BEGIN
END CONVERSATION @conversation_handle; END
COMMIT TRANSACTION END
END
Second step: Allow your TargetQueue to automatically run your procedure:
USE [MyDatabase]
ALTER QUEUE [dbo].[TargetQueue] WITH STATUS = ON , RETENTION = OFF , ACTIVATION
( STATUS = ON , --activation status
PROCEDURE_NAME = dbo.p_RecieveMessageFromTargetQueue , --procedure name MAX_QUEUE_READERS = 1 , --number of readers EXECUTE AS SELF )
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Chapter 101: Permissions and Security
Section 101.1: Assign Object Permissions to a user
In Production its good practice to secure your data and only allow operations on it to be undertaken via Stored Procedures. This means your application can't directly run CRUD operations on your data and potentially cause problems. Assigning permissions is a time-consuming, fiddly and generally onerous task. For this reason its often easier to harness some of the (considerable) power contained in the INFORMATION_SCHEMA er schema which is contained in every SQL Server database.
Instead individually assigning permissions to a user on a piece-meal basis, just run the script below, copy the output and then run it in a Query window.
SELECT 'GRANT EXEC ON core.' + r.ROUTINE_NAME + ' TO ' + <MyDatabaseUsername> FROM INFORMATION_SCHEMA.ROUTINES r WHERE r.ROUTINE_CATALOG = '<MyDataBaseName>'
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Chapter 102: Database permissions
Section 102.1: Changing permissions
GRANT SELECT ON [dbo].[someTable] TO [aUser];
REVOKE SELECT ON [dbo].[someTable] TO [aUser]; --REVOKE SELECT [dbo].[someTable] FROM [aUser]; is equivalent
DENY SELECT ON [dbo].[someTable] TO [aUser];
Section 102.2: CREATE USER
--implicitly map this user to a login of the same name as the user CREATE USER [aUser];
--explicitly mapping what login the user should be associated with CREATE USER [aUser] FOR LOGIN [aUser];
Section 102.3: CREATE ROLE
CREATE ROLE [myRole];
Section 102.4: Changing role membership
-- SQL 2005+ exec sp_addrolemember @rolename = 'myRole', @membername = 'aUser'; exec sp_droprolemember @rolename = 'myRole', @membername = 'aUser';
-- SQL 2008+ ALTER ROLE [myRole] ADD MEMBER [aUser]; ALTER ROLE [myRole] DROP MEMBER [aUser];
Note: role members can be any database-level principal. That is, you can add a role as a member in another role. Also, adding/dropping role members is idempotent. That is, attempting to add/drop will result in their presence/absence (respectively) in the role regardless of the current state of their role membership.
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Chapter 103: Row-level security
Section 103.1: RLS filter predicate
Sql Server 2016+ and Azure Sql database enables you to automatically filter rows that are returned in select statement using some predicate. This feature is called Row-level security.
First, you need a table-valued function that contains some predicate that describes what it the condition that will allow users to read data from some table:
DROP FUNCTION IF EXISTS dbo.pUserCanAccessCompany GO CREATE FUNCTION
dbo.pUserCanAccessCompany(@CompanyID int)
RETURNS TABLE WITH SCHEMABINDING AS RETURN (
SELECT 1 as canAccess WHERE
CAST(SESSION_CONTEXT(N'CompanyID') as int) = @CompanyID
)
In this example, the predicate says that only users that have a value in SESSION_CONTEXT that is matching input argument can access the company. You can put any other condition e.g. that checks database role or database_id of the current user, etc.
Most of the code above is a template that you will copy-paste. The only thing that will change here is the name and arguments of predicate and condition in WHERE clause. Now you create security policy that will apply this predicate on some table.
Now you can create security policy that will apply predicate on some table:
CREATE SECURITY POLICY dbo.CompanyAccessPolicy
ADD FILTER PREDICATE dbo.pUserCanAccessCompany(CompanyID) ON dbo.Company WITH (State=ON)
This security policy assigns predicate to company table. Whenever someone tries to read data from Company table , security policy will apply predicate on each row, pass CompanyID column as a parameter of the predicate, and predicate will evaluate should this row be returned in the result of SELECT query.
Section 103.2: Altering RLS security policy
Security policy is a group of predicates associated to tables that can be managed together. You can add, or remove predicates or turn on/off entire policy.
You can add more predicates on tables in the existing security policy.
ALTER SECURITY POLICY dbo.CompanyAccessPolicy
ADD FILTER PREDICATE dbo.pUserCanAccessCompany(CompanyID) ON dbo.Company
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You can drop some predicates from security policy:
ALTER SECURITY POLICY dbo.CompanyAccessPolicy
DROP FILTER PREDICATE ON dbo.Company
You can disable security policy
ALTER SECURITY POLICY dbo.CompanyAccessPolicy WITH ( STATE = OFF );
You can enable security policy that was disabled:
ALTER SECURITY POLICY dbo.CompanyAccessPolicy WITH ( STATE = ON );
Section 103.3: Preventing updated using RLS block predicate
Row-level security enables you to define some predicates that will control who could update rows in the table. First you need to define some table-value function that represents predicate that wll control access policy.
CREATE FUNCTION dbo.pUserCanAccessProduct(@CompanyID int) RETURNS TABLE WITH SCHEMABINDING AS RETURN (
SELECT 1 as canAccess WHERE CAST(SESSION_CONTEXT(N'CompanyID') as int) = @CompanyID )
In this example, the predicate says that only users that have a value in SESSION_CONTEXT that is matching input argument can access the company. You can put any other condition e.g. that checks database role or database_id of the current user, etc.
Most of the code above is a template that you will copy-paste. The only thing that will change here is the name and arguments of predicate and condition in WHERE clause. Now you create security policy that will apply this predicate on some table.
Now we can create security policy with the predicate that will block updates on product table if CompanyID column in table do not satisfies predicate.
CREATE SECURITY POLICY dbo.ProductAccessPolicy ADD BLOCK PREDICATE dbo.pUserCanAccessProduct(CompanyID) ON dbo.Product
This predicate will be applied on all operations. If you want to apply predicate on some operation you can write something like:
CREATE SECURITY POLICY dbo.ProductAccessPolicy ADD BLOCK PREDICATE dbo.pUserCanAccessProduct(CompanyID) ON dbo.Product AFTER INSERT
Possible options that you can add after block predicate definition are:
[ { AFTER { INSERT | UPDATE } } | { BEFORE { UPDATE | DELETE } } ]
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Chapter 104: Encryption
Optional Parameters Details
WITH PRIVATE KEY
For CREATE CERTIFICATE, a private key can be specified: (FILE='D:\Temp\CertTest\private.pvk', DECRYPTION BY PASSWORD = 'password');
Section 104.1: Encryption by certificate
CREATE CERTIFICATE My_New_Cert FROM FILE = 'D:\Temp\CertTest\certificateDER.cer' GO
Create the certificate
SELECT EncryptByCert(Cert_ID('My_New_Cert'), 'This text will get encrypted') encryption_test
Usually, you would encrypt with a symmetric key, that key would get encrypted by the asymmetric key (public key) from your certificate.
Also, note that encryption is limited to certain lengths depending on key length and returns NULL otherwise. Microsoft writes: "The limits are: a 512 bit RSA key can encrypt up to 53 bytes, a 1024 bit key can encrypt up to 117 bytes, and a 2048 bit key can encrypt up to 245 bytes."
EncryptByAsymKey has the same limits. For UNICODE this would be divided by 2 (16 bits per character), so 58 characters for a 1024 bit key.
Section 104.2: Encryption of database
USE TDE CREATE DATABASE ENCRYPTION KEY WITH ALGORITHM = AES_256 ENCRYPTION BY SERVER CERTIFICATE My_New_Cert GO
ALTER DATABASE TDE SET ENCRYPTION ON GO
This uses 'Transparent Data Encryption' (TDE)
Section 104.3: Encryption by symmetric key
-- Create the key and protect it with the cert CREATE SYMMETRIC KEY My_Sym_Key WITH ALGORITHM = AES_256 ENCRYPTION BY CERTIFICATE My_New_Cert; GO
-- open the key OPEN SYMMETRIC KEY My_Sym_Key DECRYPTION BY CERTIFICATE My_New_Cert;
-- Encrypt SELECT EncryptByKey(Key_GUID('SSN_Key_01'), 'This text will get encrypted');
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Section 104.4: Encryption by passphrase
SELECT EncryptByPassphrase('MyPassPhrase', 'This text will get encrypted')
This will also encrypt but then by passphrase instead of asymmetric(certificate) key or by an explicit symmetric key.
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Chapter 105: PHANTOM read
In database systems, isolation determines how transaction integrity is visible to other users and systems, so it defines how/when the changes made by one operation become visible to other. The phantom read may occurs when you getting data not yet commited to database.
Section 105.1: Isolation level READ UNCOMMITTED
Create a sample table on a sample database
CREATE TABLE [dbo].[Table_1](
[Id] [int] IDENTITY(1,1) NOT NULL, [title] [varchar](50) NULL, CONSTRAINT [PK_Table_1] PRIMARY KEY CLUSTERED (
[Id] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY]
Now open a First query editor (on the database) insert the code below, and execute (do not touch the --rollback) in this case you insert a row on DB but do not commit changes.
begin tran
INSERT INTO Table_1 values('Title 1')
SELECT * FROM [Test].[dbo].[Table_1]
--rollback
Now open a Second Query Editor (on the database), insert the code below and execute
begin tran
set transaction isolation level READ UNCOMMITTED
SELECT * FROM [Test].[dbo].[Table_1]
You may notice that on second editor you can see the newly created row (but not committed) from first transaction. On first editor execute the rollback (select the rollback word and execute).
-- Rollback the first transaction rollback
Execute the query on second editor and you see that the record disappear (phantom read), this occurs because you tell, to the 2nd transaction to get all rows, also the uncommitteds.
This occurs when you change the isolation level with
set transaction isolation level READ UNCOMMITTED
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Chapter 106: Filestream
FILESTREAM integrates the SQL Server Database Engine with an NTFS file system by storing varbinary(max) binary large object (BLOB) data as files on the file system. Transact-SQL statements can insert, update, query, search, and back up FILESTREAM data. Win32 file system interfaces provide streaming access to the data.
Section 106.1: Example
Source : MSDN https://technet.microsoft.com/en-us/library/bb933993(v=sql.105).aspx
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Chapter 107: bcp (bulk copy program) Utility
The bulk copy program utility (bcp) bulk copies data between an instance of Microsoft SQL Server and a data file in a user-specified format. The bcp utility can be used to import large numbers of new rows into SQL Server tables or to export data out of tables into data files.
Section 107.1: Example to Import Data without a Format File(using Native Format )
REM Truncate table (for testing) SQLCMD -Q "TRUNCATE TABLE TestDatabase.dbo.myNative;"
REM Import data bcp TestDatabase.dbo.myNative IN D:\BCP\myNative.bcp -T -n
REM Review results SQLCMD -Q "SELECT * FROM TestDatabase.dbo.myNative;"
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Chapter 108: SQL Server Evolution through dierent versions (2000 - 2016)
I am using SQL Server since 2004. I started with 2000 and now I am going to use SQL Server 2016. I created tables, views, functions, triggers, stored procedures and wrote many SQL queries but I did not use many new features from subsequent versions. I googled it but unfortunately, I did not find all the features in one place. So I gathered and validated these information from different sources and put here. I am just adding the high level information for all the versions starting from 2000 to 20
Section 108.1: SQL Server Version 2000 - 2016
The following features added in SQL Server 2000 from its previous version:
New data types were added (BIGINT, SQL_VARIANT, TABLE) 1. Instead of and for Triggers were introduced as advancement to the DDL. 2. Cascading referential integrity. 3. XML support 4. User defined functions and partition views. 5. Indexed Views (Allowing index on views with computed columns). 6.
The following features added in version 2005 from its previous version:
Enhancement in TOP clause with “WITH TIES” option. 1. Data Manipulation Commands (DML) and OUTPUT clause to get INSERTED and DELETED values 2. The PIVOT and UNPIVOT operators. 3. Exception Handling with TRY/CATCH block 4. Ranking functions 5. Common Table Expressions (CTE) 6. Common Language Runtime (Integration of .NET languages to build objects like stored procedures, triggers, 7.
functions etc.) Service Broker (Handling message between a sender and receiver in a loosely coupled manner) 8. Data Encryption (Native capabilities to support encryption of data stored in user defined databases) 9. SMTP mail 10. HTTP endpoints (Creation of endpoints using simple T-SQL statement exposing an object to be accessed over 11.
the internet) Multiple Active Result Sets (MARS).This allows a persistent database connection from a single client to have 12.
more than one active request per connection. SQL Server Integration Services (Will be used as a primary ETL (Extraction, Transformation and Loading) Tool 13. Enhancements in Analysis Services and Reporting Services. 14. Table and index partitioning. Allows partitioning of tables and indexes based on partition boundaries as 15.
specified by a PARTITION FUNCTION with individual partitions mapped to file groups via a PARTITION SCHEME.
The following features added in version 2008 from its previous version:
Enhancement in existing DATE and TIME Data Types 1. New functions like – SYSUTCDATETIME() and SYSDATETIMEOFFSET() 2. Spare Columns – To save a significant amount of disk space. 3. Large User Defined Types (up to 2 GB in size) 4. Introduced a new feature to pass a table datatype into stored procedures and functions 5. New MERGE command for INSERT, UPDATE and DELETE operations 6.
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New HierarchyID datatype 7. Spatial datatypes - To represent the physical location and shape of any geometric object. 8. Faster queries and reporting with GROUPING SETS - An extension to the GROUP BY clause. 9. Enhancement to FILESTREAM storage option 10.
The following features added in version 2008 R2 from its previous version:
PowerPivot – For processing large data sets. 1. Report Builder 3.0 2. Cloud ready 3. StreamInsight 4. Master Data Services 5. SharePoint Integration 6. DACPAC (Data-tier Application Component Packages) 7. Enhancement in other features of SQL Server 2008 8.
The following features added in version 2012 from its previous version:
Column store indexes - reduces I/O and memory utilization on large queries. 1. Pagination - pagination can be done by using “OFFSET” and “FETCH’ commands. 2. Contained database – Great feature for periodic data migrations. 3. AlwaysOn Availability Groups 4. Windows Server Core Support 5. User-Defined Server Roles 6. Big Data Support 7. PowerView 8. SQL Azure Enhancements 9. Tabular Model (SSAS) 10. DQS Data quality services 11. File Table - an enhancement to the FILESTREAM feature which was introduced in 2008. 12. Enhancement in Error Handling including THROW statement 13. Improvement to SQL Server Management Studio Debugging a. SQL Server 2012 introduces more options to 14.
control breakpoints. b. Improvements to debug-mode windows c. Enhancement in IntelliSense - like Inserting Code Snippets.
The following features added in version 2014 from its previous version:
In-Memory OLTP Engine – Improves performance up to 20 times. 1. AlwaysOn Enhancements 2. Buffer Pool Extension 3. Hybrid Cloud Features 4. Enhancement in Column store Indexes (like Updatable Column store Indexes) 5. Query Handling Enhancements (like parallel SELECT INTO) 6. Power BI for Office 365 Integration 7. Delayed durability 8. Enhancements for Database Backups 9.
The following features added in version 2016 from its previous version:
Always Encrypted - Always Encrypted is designed to protect data at rest or in motion. 1. Real-time Operational Analytics 2. PolyBase into SQL Server 3. Native JSON Support 4.
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Query Store 5. Enhancements to AlwaysOn 6. Enhanced In-Memory OLTP 7. Multiple TempDB Database Files 8. Stretch Database 9. Row Level Security 10. In-Memory Enhancements 11.
T-SQL Enhancements or new additions in SQL Server 2016
TRUNCATE TABLE with PARTITION 1.
DROP IF EXISTS 2.
STRING_SPLIT and STRING_ESCAPE Functions 3.
ALTER TABLE can now alter many columns while the table remains online, using WITH (ONLINE = ON | OFF). 4.
MAXDOP for DBCC CHECKDB, DBCC CHECKTABLE and DBCC CHECKFILEGROUP 5.
ALTER DATABASE SET AUTOGROW_SINGLE_FILE 6.
ALTER DATABASE SET AUTOGROW_ALL_FILES 7.
COMPRESS and DECOMPRESS Functions 8.
FORMATMESSAGE Statement 9.
2016 introduces 8 more properties with SERVERPROPERTY 10.
a. InstanceDefaultDataPath
b. InstanceDefaultLogPath
c. ProductBuild
d. ProductBuildType
e. ProductMajorVersion
f. ProductMinorVersion
g. ProductUpdateLevel
h. ProductUpdateReference
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Chapter 109: SQL Server Management Studio (SSMS)
SQL Server Management Studio (SSMS) is a tool to manage and administer SQL Server and SQL Database.
SSMS is offered free of charge by Microsoft.
SSMS Documentation is available.
Section 109.1: Refreshing the IntelliSense cache
When objects are created or modified they are not automatically available for IntelliSense. To make them available to IntelliSense the local cache has to be refreshed.
Within an query editor window either press Ctrl + Shift + R or select Edit | IntelliSense | Refresh Local Cache from the menu.
After this all changes since the last refresh will be available to IntelliSense.
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Chapter 110: Managing Azure SQL Database
Section 110.1: Find service tier information for Azure SQL Database
Azure SQL Database has different editions and performance tiers.
You can find version, edition (basic, standard, or premium), and service objective (S0,S1,P4,P11, etc.) of SQL Database that is running as a service in Azure using the following statements:
select @@version SELECT DATABASEPROPERTYEX('Wwi', 'EDITION') SELECT DATABASEPROPERTYEX('Wwi', 'ServiceObjective')
Section 110.2: Change service tier of Azure SQL Database
You can scale-up or scale-down Azure SQL database using ALTER DATABASE statement:
ALTER DATABASE WWI MODIFY (SERVICE_OBJECTIVE = 'P6') -- or ALTER DATABASE CURRENT MODIFY (SERVICE_OBJECTIVE = 'P2')
If you try to change service level while changing service level of the current database is still in progress you wil get the following error:
Msg 40802, Level 16, State 1, Line 1 A service objective assignment on server '......' and database '.......' is already in progress. Please wait until the service objective assignment state for the database is marked as 'Completed'.
Re-run your ALTER DATABASE statement when transition period finishes.
Section 110.3: Replication of Azure SQL Database
You can create a secondary replica of database with the same name on another Azure SQL Server, making the local database primary, and begins asynchronously replicating data from the primary to the new secondary.
ALTER DATABASE <<mydb>> ADD SECONDARY ON SERVER <<secondaryserver>> WITH ( ALLOW_CONNECTIONS = ALL )
Target server may be in another data center (usable for geo-replication). If a database with the same name already exists on the target server, the command will fail. The command is executed on the master database on the server hosting the local database that will become the primary. When ALLOW_CONNECTIONS is set to ALL (it is set to NO by default), secondary replica will be a read-only database that will allow all logins with the appropriate permissions to connect.
Secondary database replica might be promoted to primary using the following command:
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ALTER DATABASE mydb FAILOVER
You can remove the secondary database on secondary server:
ALTER DATABASE <<mydb>> REMOVE SECONDARY ON SERVER <<testsecondaryserver>>
Section 110.4: Create Azure SQL Database in Elastic pool
You can put your azure SQL Database in SQL elastic pool:
CREATE DATABASE wwi ( SERVICE_OBJECTIVE = ELASTIC_POOL ( name = mypool1 ) )
You can create copy of an existing database and place it in some elastic pool:
CREATE DATABASE wwi AS COPY OF myserver.WideWorldImporters ( SERVICE_OBJECTIVE = ELASTIC_POOL ( name = mypool1 ) )
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Chapter 111: System database - TempDb
Section 111.1: Identify TempDb usage
Following query will provide information about TempDb usage. Analyzing the counts you can identify which thing is impacting TempDb
SELECT
SUM (user_object_reserved_page_count)*8 as usr_obj_kb, SUM (internal_object_reserved_page_count)*8 as internal_obj_kb, SUM (version_store_reserved_page_count)*8 as version_store_kb, SUM (unallocated_extent_page_count)*8 as freespace_kb, SUM (mixed_extent_page_count)*8 as mixedextent_kb FROM sys.dm_db_file_space_usage
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Section 111.2: TempDB database details
Below query can be used to get TempDB database details:
USE [MASTER] SELECT * FROM sys.databases WHERE database_id = 2
OR
USE [MASTER] SELECT * FROM sys.master_files WHERE database_id = 2
With the help of below DMV, you can check how much TempDb space does your session is using. This query is quite helpful while debugging TempDb issues
SELECT * FROM sys.dm_db_session_space_usage WHERE session_id = @@SPID
Appendix A: Microsoft SQL Server Management Studio Shortcut Keys
Section A.1: Shortcut Examples
Open a new Query Window with current connection ( Ctrl + N ) 1. Toggle between opened tabs ( Ctrl + Tab ) 2. Show/Hide Results pane ( Ctrl + R ) 3. Execute highlighted query ( Ctrl + E ) 4. Make selected text uppercase or lowercase ( Ctrl + Shift + U , Ctrl + Shift + L ) 5. Intellisense list member and complete word ( Ctrl + Space , Tab ) 6. Go to line ( Ctrl + G ) 7. close a tab in SQL Server Managament Studio ( Ctrl + F4 ) 8.
Section A.2: Menu Activation Keyboard Shortcuts
Move to the SQL Server Management Studio menu bar ( ALT ) 1. Activate the menu for a tool component ( ALT + HYPHEN ) 2. Display the context menu ( SHIFT + F ) 3. Display the New File dialog box to create a file ( CTRL + N ) 4. Display the Open Project dialog box to open an existing project ( CTRL + SHIFT + 0 ) 5. Display the Add New Item dialog box to add a new file to the current project ( CTRL + SHIFT + A ) 6. Display the Add Existing Item dialog box to add an existing file to the current project 7.
( CTRL + SHIFT + A ) Display the Query Designer ( CTRL + SHIFT + Q ) 8. Close a menu or dialog box, canceling the action ( ESC ) 9.
Section A.3: Custom keyboard shortcuts
Go to Tools -> Options. Go to Environment -> Keyboard -> Query Shortcuts
On the right side you can see some shortcuts which are by default in SSMS. Now if you need to add a new one, just click on any column under Stored Procedure column.
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Click OK. Now please go to a query window and select the stored procedure then press CTRL+3, it will show the stored procedure result.
Now if you need to select all the records from a table when you select the table and press CTRL+5(You can select any key). You can make the shortcut as follows.
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Now go ahead and select the table name from the query window and press CTRL+4(The key we selected), it will give you the result.
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Credits
Thank you greatly to all the people from Stack Overflow Documentation who helped provide this content, more changes can be sent to web@petercv.com for new content to be published or updated
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Chapters 5, 11, 20, 26, 27, 28, 29, 30, 31, 34, 41, 52, 55, 80, 81, 85, 86, 89, 91, 93, 94, 96, 98, 99, 103 and 110 juergen d Chapter 23 jyao Chapter 51 K48 Chapter 1 Kane Chapter 62 Kannan Kandasamy Chapters 7, 35 and 44 Karthikeyan Chapter 12 Keith Hall Chapters 8, 32 and 36 Kiran Ukande Chapters 23 and 25 kolunar Chapters 45 and 47 Kritner Chapters 7, 9, 39 and 54 Laughing Vergil Chapters 1, 2, 7, 14 and 51 lord5et Chapter 21 LowlyDBA Chapters 33, 39 and 51
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Luis Bosquez Chapter 83 M.Ali Chapters 13 and 108 Mahesh Dahal Chapter 1 Malt Chapter 1 Mani Chapter 82 MarmiK Chapters 46 and 107 martinshort Chapter 15 MasterBob Chapter 52 Matas Vaitkevicius Chapters 2, 15, 21, 23, 50 and 65 Matej Chapters 12 and 100 Matt Chapters 1 and 78 Max Chapters 1, 15, 18 and 105 Merenix Chapter 88 Metanormal Chapter 90 Michael Stum Chapter 15 Mihai Chapter 1 Mono Chapter 26 Monty Wild Chapter 36 Moshiour Chapter 16 MrE Chapter 25 Mspaja Chapter 69 Mudassir Hasan Chapter 1 n00b Chapters 1 and 15 Nathan Skerl Chapter 50 Neil Kennedy Chapter 92 New Chapters 45 and 70 Nick Chapters 1 and 9 Nick.McDermaid Chapter 37 Oluwafemi Chapters 61 and 74 OzrenTkalcecKrznaric Chapters 1, 33 and 73 Pat Chapter 87 Paul Bambury Chapter 22 Peter Tirrell Chapter 1 Phrancis Chapters 1, 8, 9, 33, 41, 51, 62, 63 and 67 Pirate X Chapter 50 podiluska Chapters 7 and 21 Prateek Chapter 1 Pரத◌ீப◌ Chapters 6 and 52 Raghu Ariga Chapter 106 Raidri Chapter 41 Ram Grandhi Chapter 33 Randall Chapter 53 ravindra Chapter 20 Rhumborl Chapter 51 Robert Columbia Chapters 15 and 17 Ross Presser Chapter 41 Rubenisme Chapter 104 S.Karras Chapter 39 Sam Chapters 1 and 22 scsimon Chapters 12, 39, 50 and 51 Sender Chapter 80 Shaneis Chapter 1 sheraz mirza Chapter 95
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Sibeesh Venu Chapter 112 Siyual Chapters 9 and 10 Soukai Chapter 9 spaghettidba Chapter 51 sqlandmore.com Chapter 72 SQLMason Chapter 36 sqluser Chapter 56 Susang Chapter 49 Tab Alleman Chapter 12 takrl Chapter 41 Taryn Chapter 25 Techie Chapter 75 TheGameiswar Chapter 40 Thuta Aung Chapter 1 Tom V Chapter 59 Tot Zam Chapters 1, 15, 17 and 51 TZHX Chapter 51 Uberzen1 Chapters 1 and 20 UnhandledExcepSean Chapter 9 user1690166 Chapter 25 user_0 Chapters 1 and 85 Vexator Chapter 43 Vikas Vaidya Chapter 14 Vladimir Oselsky Chapter 92 Wolfgang Chapters 11 and 32 Zohar Peled Chapters 4, 7, 9, 41, 61 and 66
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