SELECT * FROM cms_user WHERE age=NULL;
Empty set (0.03 sec)
查询表中记录age值为null
mysql> SELECT * FROM cms_user WHERE age<=>NULL;
+----+----------+----------+-------------+------------+----------+-------+------+
| id | username | password | email | regTime | face | proId | age |
+----+----------+----------+-------------+------------+----------+-------+------+
| 12 | test1 | test1 |sui@qq.com | 1419811708 | user.jpg | 1 | NULL |
+----+----------+----------+-------------+------------+----------+-------+------+
1 row in set (0.03 sec) 查询表中的 null 值使用 <=> 使用: is null 和 is not null
ELECT * FROM cms_user WHERE age IS NULL;
+----+----------+----------+-------------+------------+----------+-------+------+
| id | username | password | email | regTime | face | proId | age |
+----+----------+----------+-------------+------------+----------+-------+------+
| 12 | test1 | test1 | user@qq.com | 1419811708 | user.jpg | 1 | NULL |
+----+----------+----------+-------------+------------+----------+-------+------+
1 row in set (0.00 sec)
IS NOT NULL
mysql> SELECT * FROM cms_user WHERE age IS NOT NULL;