有一張很老的數據表，時間戳格式為varchar，字段如下：idbigintnamevarchar(200)create_timevarchar(200)//索引KEY`IDX_CREATED`(`create_time`),數據約500多萬，現在引出發現的問題，一條sql語句效率非常的低：selectid,namefromtwherecreate_time>1434115807296orderbycreate_timelimit1000;本機測試200s，執行計劃：>explainselectid,namefromtwherecreate_time>1434115807296orderbycreate_timelimit1000;+----+-------------+-------+-------+---------------+---------------+---------+------+------+-------------+|id|select_type|table|type|possible_keys|key|key_len|ref|rows|Extra|+----+-------------+-------+-------+---------------+---------------+---------+------+------+-------------+|1|SIMPLE|User|index|IDX_CREATED|IDX_CREATED|63|NULL|1000|Usingwhere|+----+-------------+-------+-------+---------------+---------------+---------+------+------+-------------+1rowinset(0.00sec)如果去掉limit:selectid,namefromtwherecreate_time>1434115807296orderbycreate_time執行時間5s，執行計劃：>explainselectid,namefromtwherecreate_time>1434115807296orderbycreate_time+----+-------------+-------+------+---------------+------+---------+------+---------+-----------------------------+|id|select_type|table|type|possible_keys|key|key_len|ref|rows|Extra|+----+-------------+-------+------+---------------+------+---------+------+---------+-----------------------------+|1|SIMPLE|User|ALL|IDX_CREATED|NULL|NULL|NULL|4858500|Usingwhere;Usingfilesort|+----+-------------+-------+------+---------------+------+---------+------+---------+-----------------------------+1rowinset(0.00sec)一個index查詢竟然比ALL&filesort查詢慢這么多？請MySQL達人指教