IS
This page is part of MariaDB's Documentation.
The parent of this page is: SQL Operators for MariaDB Xpand
Topics on this page:
Overview
Boolean comparison.
USAGE
expression IS TRUE|FALSE|UNKNOWN
Value Name | Description |
|---|---|
| A value expression |
DETAILS
The IS operator returns a truth value for one of 3 boolean comparisons:
x IS TRUEchecks if the expression evaluates toTRUE(a non-zero value)x IS FALSEchecks if the expression evaluates toFALSE(a zero value)x IS UNKNOWNchecks if the expression has no known value (isNULL)
The return value is always 1 (true) or 0 (false). Evaluating a NULL value does not return NULL because this operator considers it to be UNKNOWN and never TRUE or FALSE.
See IS NOT for the negated version of these comparisons.
EXAMPLES
SELECT 1 IS TRUE, 1 IS FALSE, 1 IS UNKNOWN;
+-----------+------------+--------------+
| 1 IS TRUE | 1 IS FALSE | 1 IS UNKNOWN |
+-----------+------------+--------------+
| 1 | 0 | 0 |
+-----------+------------+--------------+
SELECT 0 IS TRUE, 0 IS FALSE, 0 IS UNKNOWN;
+-----------+------------+--------------+
| 0 IS TRUE | 0 IS FALSE | 0 IS UNKNOWN |
+-----------+------------+--------------+
| 0 | 1 | 0 |
+-----------+------------+--------------+
SELECT NULL IS TRUE, NULL IS FALSE, NULL IS UNKNOWN;
+--------------+---------------+-----------------+
| NULL IS TRUE | NULL IS FALSE | NULL IS UNKNOWN |
+--------------+---------------+-----------------+
| 0 | 0 | 1 |
+--------------+---------------+-----------------+
SELECT 42 = TRUE, 42 IS TRUE;
+-----------+------------+
| 42 = TRUE | 42 IS TRUE |
+-----------+------------+
| 0 | 1 |
+-----------+------------+