Boolean test conditions

Boolean test conditions are used to check whether the logical value of an expression is TRUE, FALSE, or UNKNOWN.

Syntax

expr IS [ NOT ] { TRUE | FALSE | UNKNOWN }

Usage instructions

• IS TRUE: Returns TRUE if the expression is TRUE, and FALSE otherwise.
• IS FALSE: Returns TRUE if the expression is FALSE; otherwise, returns FALSE.
• IS UNKNOWN: Returns TRUE if the expression is UNKNOWN, and FALSE otherwise.
• IS NOT TRUE, IS NOT FALSE, and IS NOT UNKNOWN are the negations of the corresponding conditions.

Examples

obclient> SELECT 1 IS TRUE AS result;
+--------+
| result |
+--------+
|      1 |
+--------+
1 row in set

obclient> SELECT 0 IS FALSE AS result;
+--------+
| result |
+--------+
|      1 |
+--------+
1 row in set

obclient> SELECT NULL IS UNKNOWN AS result;
+--------+
| result |
+--------+
|      1 |
+--------+
1 row in set