SQL Server 2012 introduced a new logical function called “IIF” and here, I am going to share basic syntax and use of this function.

The primary purpose of this function is to check the Boolean condition. If the condition is true, it returns a true value. Otherwise, it returns the false value.

Using this function, you can validate and return value in a single line of code and don’t require to use IF-ELSE.

The Syntax of IIF:

IIF ( boolean_expression, true_value, false_value )

Example ONE:

DECLARE @no1 int = 808;
DECLARE @no2 int = 1600;
SELECT IIF ( @no1 > @no2, 'TRUE', 'FALSE' ) AS Result;

Result
-------
FALSE

Example TWO:

DECLARE @no1 int = 808;
DECLARE @no2 int = 1600;
SELECT IIF ( @no1 > @no2, NULL, NULL ) AS Result;

--Result: Error (Both NULL constant is not allowed)

Example THREE:

DECLARE @no1 int = 808;
DECLARE @no2 int = 1600;
SELECT IIF ( @no1 > @no2, NULL, 'Else' ) AS Result;

Result
------
Else

Example of Nested IIF:

DECLARE @Score int = 88;
SELECT IIF ( @Score> 90, 'A Grade', IIF(@Score>=80 And @Score<=90,'B Grade','C Grade')) AS Result;

Result
-------
B Grade