mysql> desc t; +-------+-----------+------+-----+-------------------+-----------------------------+ | Field | Type | Null | Key | Default | Extra | +-------+-----------+------+-----+-------------------+-----------------------------+ | id | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP | +-------+-----------+------+-----+-------------------+-----------------------------+ 1 row in set (0.00 sec)
mysql> insert into t values(null); "null" null Query OK, 1 row affected (0.00 sec)
mysql> select * from t; +--------------------------+ | id | +--------------------------+ | 2013-12-18 00:08:41 | +--------------------------+ 1 row in set (0.00 sec)