SQL Server NULLIF() Function

Compare two expressions:

SELECT NULLIF(25, 25);

Definition and Usage

The NULLIF() function returns NULL if two expressions are equal, otherwise it returns the first expression.

NULLIF( expr1, expr2)

Parameter	Description
expr1, expr2	Required. The two expressions to be compared

Works in:	SQL Server (starting with 2008), Azure SQL Database, Azure SQL Data Warehouse, Parallel Data Warehouse

Compare two expressions:

SELECT NULLIF('Hello', 'Hello');

Compare two expressions:

SELECT NULLIF('Hello', 'world');

Compare two expressions:

SELECT NULLIF('2017-08-25', '2017-08-25');