Tests whether a value is NULL. See also NULL Values in MariaDB.
Some ODBC applications use the syntax auto_increment_field IS NOT NULL to find the latest row that was inserted with an autogenerated key value. If your applications need this, you can set the variable to 1.
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IS NULLSELECT 1 IS NULL, 0 IS NULL, NULL IS NULL;
+-----------+-----------+--------------+
| 1 IS NULL | 0 IS NULL | NULL IS NULL |
+-----------+-----------+--------------+
| 0 | 0 | 1 |
+-----------+-----------+--------------+SET @@sql_auto_is_null=1;
CREATE TABLE t1 (auto_increment_column INT NOT NULL AUTO_INCREMENT PRIMARY KEY);
INSERT INTO t1 VALUES (NULL);
SELECT * FROM t1 WHERE auto_increment_column IS NULL;
+-----------------------+
| auto_increment_column |
+-----------------------+
| 1 |
+-----------------------+