NULLIF function in SQL Server

NULLIF: 

• It will accept only  two parameters. 
• If both are not equal then it will return first value.

Example : SELECT NULLIF(1,2)
O/P        : 1
In the above syntax, the first argument  can not be null. Then it will return  1


Example : SELECT NULLIF(null,1)
O/P        : Error    
The above query throws error because the first argument is null. The first argument can not be null.


Example : SEELCT NULLIF(2,2)
O/P        : null
In the above query, it will return null value because, the arguments should not be equal. The argument should be different.