ISNULL

Declaration

ISNULL(expr)

Description

If the parameter expr is NULL, then the return value of ISNULL() is 1, otherwise it is 0.

The ISNULL() function can be used instead of the equals sign (=) to determine whether a value is NULL. (Using the equals sign to compare a value with NULL always returns NULL) The ISNULL() function shares some characteristics with the IS NULL comparison operator. For more information about comparison operators, see Comparison Operators.

Examples

SELECT ISNULL(null), ISNULL('test'), ISNULL(123.456), ISNULL('10:00');
+--------------+----------------+-----------------+-----------------+
| ISNULL(null) | ISNULL('test') | ISNULL(123.456) | ISNULL('10:00') |
+--------------+----------------+-----------------+-----------------+
|            1 |              0 |               0 |               0 |
+--------------+----------------+-----------------+-----------------+
1 row in set (0.001 sec)

SELECT ISNULL(null+1);
+----------------+
| ISNULL(null+1) |
+----------------+
|              1 |
+----------------+
1 row in set (0.001 sec)