"IS NULL" - Testing NULL Values in SQL Server

Q

How To Test NULL Values Properly in SQL Server Transact-SQL?

✍: FYIcenter.com

A

From previous tutorials, you learned that comparing expressions with NULL will always result NULL. So you can not use comparison operators to test if an expression represents a NULL value or not.

To test expressions for NULL values, you should use one of the following special operators:

expression IS NULL 
-- Returns TRUE if the expression is a NULL value

expression IS NOT NULL
-- Returns TRUE if the expression is not a NULL value

The tutorial script below shows you how to use IS NULL and IS NOT NULL:

IF 0 IS NULL PRINT 'TRUE'
ELSE PRINT 'FALSE';
GO
FALSE

IF NULL IS NULL PRINT 'TRUE'
ELSE PRINT 'FALSE';
GO
TRUE

IF 1+NULL IS NULL PRINT 'TRUE'
ELSE PRINT 'FALSE';
GO
TRUE

IF 'NULL' IS NOT NULL PRINT 'TRUE'
ELSE PRINT 'FALSE';
GO
TRUE

 

Working with NULL Values in SQL Server Transact-SQL

⇒⇒SQL Server Transact-SQL Tutorials

2017-02-03, 218👍, 0💬