小编lpa*_*lpa的帖子

简单查询但无法摆脱“using filesort”：

CREATE TABLE IF NOT EXISTS `online` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `uid` int(11) NOT NULL,
  `expiration` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `uid` (`uid`),
  KEY `expiration` (`expiration`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=1925234 ;

mysql> explain SELECT i.id, i.uid, i.expiration, u.nick, u.mainpicture
    -> FROM online i join usertable u on i.uid = u.id
    -> order by i.expiration DESC limit 0,12;

+----+-------------+-------+--------+---------------+---------+---------+----------------+------+----------------+
| id | select_type | table | type   | possible_keys | key     | key_len | ref …