NULLIF

Compares two expressions. If the expressions are not equal, the function returns the first expression (expression1). If the expressions are equal, the function returns null.

Behavior type

Immutable

Syntax

NULLIF( expression1, expression2 )

Parameters

expression1

Is a value of any data type.

expression2

Must have the same data type as *expr1 *or a type that can be implicitly cast to match expression1. The result has the same type as expression1.

Examples

The following series of statements illustrates one simple use of the NULLIF function.

Creates a single-column table t and insert some values:

CREATE TABLE t (x TIMESTAMPTZ);
INSERT INTO t VALUES('2009-09-04 09:14:00-04');
INSERT INTO t VALUES('2010-09-04 09:14:00-04');

Issue a select statement:

SELECT x, NULLIF(x, '2009-09-04 09:14:00 EDT') FROM t;
           x            |         nullif
------------------------+------------------------
 2009-09-04 09:14:00-04 |
 2010-09-04 09:14:00-04 | 2010-09-04 09:14:00-04
SELECT NULLIF(1, 2);
 NULLIF
--------
      1
(1 row)
SELECT NULLIF(1, 1);
 NULLIF
--------
(1 row)
SELECT NULLIF(20.45, 50.80);
 NULLIF
--------
  20.45
(1 row)