IS NOT NULLTests whether a value is not NULL. See also NULL Values in MariaDB.
This page is licensed: GPLv2, originally from
SELECT 1 IS NOT NULL, 0 IS NOT NULL, NULL IS NOT NULL;
+---------------+---------------+------------------+
| 1 IS NOT NULL | 0 IS NOT NULL | NULL IS NOT NULL |
+---------------+---------------+------------------+
| 1 | 1 | 0 |
+---------------+---------------+------------------+