nullif

description

Syntax

nullif(expr1, expr2)

If the two parameters are equal, null is returned. Otherwise, the value of the first parameter is returned. It has the same effect as the following case when

CASE
     WHEN expr1 = expr2 THEN NULL
     ELSE expr1
END

example

mysql> select nullif(1,1);
+--------------+
| nullif(1, 1) |
+--------------+
|         NULL |
+--------------+
mysql> select nullif(1,0);
+--------------+
| nullif(1, 0) |
+--------------+
|            1 |
+--------------+

keywords

NULLIF