SET ANSI_NULLS (Transact-SQL)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Azure Synapse Analytics
Analytics Platform System (PDW)
Specifies ISO compliant behavior of the Equals (=) and Not Equal To (<>) comparison operators when they are used with null values in SQL Server.
Note
SET ANSI_NULLS OFF and the ANSI_NULLS OFF database option are deprecated. Starting with SQL Server 2017 (14.x), ANSI_NULLS is always set to ON. Deprecated features shouldn't be used in new applications. For more information, see Deprecated Database Engine features in SQL Server 2017.
Transact-SQL syntax conventions
Syntax
Syntax for SQL Server, serverless SQL pool in Azure Synapse Analytics, Microsoft Fabric
SET ANSI_NULLS { ON | OFF }
Syntax for Azure Synapse Analytics and Analytics Platform System (PDW)
SET ANSI_NULLS ON
Remarks
When ANSI_NULLS is ON, a SELECT statement that uses WHERE column_name = NULL returns zero rows even if there are NULL values in column_name. A SELECT statement that uses WHERE column_name <> NULL returns zero rows even if there are non-NULL values in column_name.
When ANSI_NULLS is OFF, the Equals (=) and Not Equal To (<>) comparison operators do not follow the ISO standard. A SELECT statement that uses WHERE column_name = NULL returns the rows that have null values in column_name. A SELECT statement that uses WHERE column_name <> NULL returns the rows that have non-NULL values in the column. Also, a SELECT statement that uses WHERE column_name <> XYZ_value returns all rows that are not XYZ_value and that are not NULL.
When ANSI_NULLS is ON, all comparisons against a null value evaluate to UNKNOWN. When SET ANSI_NULLS is OFF, comparisons of all data against a null value evaluate to TRUE if the data value is NULL. If SET ANSI_NULLS is not specified, the setting of the ANSI_NULLS option of the current database applies. For more information about the ANSI_NULLS database option, see ALTER DATABASE (Transact-SQL).
The following table shows how the setting of ANSI_NULLS affects the results of a number of Boolean expressions using null and non-null values.
| Boolean Expression | SET ANSI_NULLS ON | SET ANSI_NULLS OFF |
|---|---|---|
NULL = NULL |
UNKNOWN | TRUE |
1 = NULL |
UNKNOWN | FALSE |
NULL <> NULL |
UNKNOWN | FALSE |
1 <> NULL |
UNKNOWN | TRUE |
NULL > NULL |
UNKNOWN | UNKNOWN |
1 > NULL |
UNKNOWN | UNKNOWN |
NULL IS NULL |
TRUE | TRUE |
1 IS NULL |
FALSE | FALSE |
NULL IS NOT NULL |
FALSE | FALSE |
1 IS NOT NULL |
TRUE | TRUE |
SET ANSI_NULLS ON affects a comparison only if one of the operands of the comparison is either a variable that is NULL or a literal NULL. If both sides of the comparison are columns or compound expressions, the setting does not affect the comparison.
For a script to work as intended, regardless of the ANSI_NULLS database option or the setting of SET ANSI_NULLS, use IS NULL and IS NOT NULL in comparisons that might contain null values.
ANSI_NULLS should be set to ON for executing distributed queries.
ANSI_NULLS must also be ON when you are creating or changing indexes on computed columns or indexed views. If SET ANSI_NULLS is OFF, any CREATE, UPDATE, INSERT, and DELETE statements on tables with indexes on computed columns or indexed views will fail. SQL Server returns an error that lists all SET options that violate the required values. Also, when you execute a SELECT statement, if SET ANSI_NULLS is OFF, SQL Server ignores the index values on computed columns or views and resolve the select operation as if there were no such indexes on the tables or views.
Note
ANSI_NULLS is one of seven SET options that must be set to required values when dealing with indexes on computed columns or indexed views. The options ANSI_PADDING, ANSI_WARNINGS, ARITHABORT, QUOTED_IDENTIFIER, and CONCAT_NULL_YIELDS_NULL must also be set to ON, and NUMERIC_ROUNDABORT must be set to OFF.
The SQL Server Native Client ODBC driver and SQL Server Native Client OLE DB Provider for SQL Server automatically set ANSI_NULLS to ON when connecting. This setting can be configured in ODBC data sources, in ODBC connection attributes, or in OLE DB connection properties that are set in the application before connecting to an instance of SQL Server. The default for SET ANSI_NULLS is OFF.
When ANSI_DEFAULTS is ON, ANSI_NULLS is enabled.
The setting of ANSI_NULLS is defined at execute or run time and not at parse time.
To view the current setting for this setting, run the following query:
DECLARE @ANSI_NULLS VARCHAR(3) = 'OFF';
IF ( (32 & @@OPTIONS) = 32 ) SET @ANSI_NULLS = 'ON';
SELECT @ANSI_NULLS AS ANSI_NULLS;
Permissions
Requires membership in the public role.
Examples
The following example uses the Equals (=) and Not Equal To (<>) comparison operators to make comparisons with NULL and non-null values in a table. The example also shows that IS NULL is not affected by the SET ANSI_NULLS setting.
-- Create table t1 and insert values.
CREATE TABLE dbo.t1 (a INT NULL);
INSERT INTO dbo.t1 values (NULL),(0),(1);
GO
-- Print message and perform SELECT statements.
PRINT 'Testing default setting';
DECLARE @varname int;
SET @varname = NULL;
SELECT a
FROM t1
WHERE a = @varname;
SELECT a
FROM t1
WHERE a <> @varname;
SELECT a
FROM t1
WHERE a IS NULL;
GO
Now set ANSI_NULLS to ON and test.
PRINT 'Testing ANSI_NULLS ON';
SET ANSI_NULLS ON;
GO
DECLARE @varname int;
SET @varname = NULL
SELECT a
FROM t1
WHERE a = @varname;
SELECT a
FROM t1
WHERE a <> @varname;
SELECT a
FROM t1
WHERE a IS NULL;
GO
Now set ANSI_NULLS to OFF and test.
PRINT 'Testing ANSI_NULLS OFF';
SET ANSI_NULLS OFF;
GO
DECLARE @varname int;
SET @varname = NULL;
SELECT a
FROM t1
WHERE a = @varname;
SELECT a
FROM t1
WHERE a <> @varname;
SELECT a
FROM t1
WHERE a IS NULL;
GO
-- Drop table t1.
DROP TABLE dbo.t1;