mysql> explain category;
+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| catid | int(11)     | NO   | PRI | NULL    | auto_increment |
| name  | varchar(30) | YES  | MUL | NULL    |                |
+-------+-------------+------+-----+---------+----------------+