NULLIF

Purpose

This function compares two expressions. If expr1 is equal to expr2, it returns NULL. Otherwise, it returns expr1.

Syntax

NULLIF(expr1, expr2)

Parameters

Return type

• If both expr1 and expr2 are numeric data types, the database determines the data type with higher precedence, implicitly converts the other expression to this data type, and returns the data type.

• If expr1 is equal to expr2 or expr1 is NULL, it returns NULL.

• If expr1 is not equal to expr2, it returns the data type of expr1.

Examples

Compare 3+4 and 6+1 to see if they are equal.

obclient> SELECT NULLIF(3+4,6+1) FROM DUAL;
+-----------------+
| NULLIF(3+4,6+1) |
+-----------------+
|            NULL |
+-----------------+
1 row in set