NULLIF

The NULLIF() function compares two expressions and returns NULL if they are equal. Otherwise, the first expression is returned.

Syntax

IF( <expr1>, <expr2>)

Arguments

Arguments	Description
<expr1>	Any general expression of any data type.
<expr2>	Any general expression that evaluates to the same data type as <expr1>.

Return Type

The data type of the returned value is the data type of <expr1>.

Examples

SELECT a, b, NULLIF(a, b) FROM t;
+------+------+--------------+
| a    | b    | NULLIF(a, b) |
+------+------+--------------+
|    0 |    0 |         NULL |
|    0 |    1 |            0 |
|    0 | NULL |            0 |
|    1 |    0 |            1 |
|    1 |    1 |         NULL |
|    1 | NULL |            1 |
| NULL |    0 |         NULL |
| NULL |    1 |         NULL |
| NULL | NULL |         NULL |
+------+------+--------------+