mysql> describe group_member;
+-----------+------------+------+-----+---------+-------+
| Field     | Type       | Null | Key | Default | Extra |
+-----------+------------+------+-----+---------+-------+
| community | bigint(10) | NO   | PRI |         |       | 
| member    | bigint(10) | NO   | PRI |         |       | 
| ctime     | datetime   | NO   |     |         |       | 
| tutor     | tinyint(1) | NO   |     | 0       |       | 
+-----------+------------+------+-----+---------+-------+
4 rows in set (0.00 sec)