NULLIF function - AWS Clean Rooms
SyntaxArgumentsExamples

NULLIF function

Compares two arguments and returns null if the arguments are equal. If they aren't equal, the first argument is returned.

Syntax

The NULLIF expression compares two arguments and returns null if the arguments are equal. If they aren't equal, the first argument is returned. This expression is the inverse of the NVL or COALESCE expression.

NULLIF ( expression1, expression2 )

Arguments

expression1, expression2

The target columns or expressions that are compared. The return type is the same as the type of the first expression. The default column name of the NULLIF result is the column name of the first expression.

Examples

In the following example, the query returns the string first because the arguments are not equal.

SELECT NULLIF('first', 'second');

case
-------
first

In the following example, the query returns NULL because the string literal arguments are equal.

SELECT NULLIF('first', 'first');

case
-------
NULL

In the following example, the query returns 1 because the integer arguments are not equal.

SELECT NULLIF(1, 2);

case
-------
1

In the following example, the query returns NULL because the integer arguments are equal.

SELECT NULLIF(1, 1);

case
-------
NULL

In the following example, the query returns null when the LISTID and SALESID values match:

select nullif(listid,salesid), salesid
from sales where salesid<10 order by 1, 2 desc;

listid  | salesid
--------+---------
     4  |       2
     5  |       4
     5  |       3
     6  |       5
     10 |       9
     10 |       8
     10 |       7
     10 |       6
        |       1
(9 rows)