使用纯索引子查询优化MySQL的分页查询速度

像这样的查询往往会耗费十几秒的时间

SELECT * FROM news WHERE cat_id = 4 ORDER BY id DESC LIMIT150000, 10

改进后

SELECT  id, value, LENGTH(stuffing) AS len FROM    t_limit ORDER BY id LIMIT 150000, 10

仍然需要数秒, 但是, 如果将ID作为子查询

SELECT  l.id, value, LENGTH(stuffing) AS len 
  FROM    ( SELECT  id FROM    t_limit ORDER BY id LIMIT 150000, 10) o
  JOIN t_limit l ON      l.id = o.id 
ORDER BY l.id

这样查询在数十毫秒就可以完成. 具体的解释看 MySQL ORDER BY / LIMIT performance: late row lookups

posted on 2012-03-22 12:37  Milton  阅读(298)  评论(0)  编辑  收藏  举报

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