使用Left Join的MySQL查询太慢

问题描述：

查询:

   select `r`.`id` as `id` 
     from `tbl_rls` as `r` 
left join `tblc_comment_manager` as `cm` on `cm`.`rlsc_id` != `r`.`id`

两个表都有8k条记录，但是为什么它却很慢，需要2-3分钟，有时还要花更多时间?

Both tables have 8k records but why is it very slow, taking 2-3 minutes and more sometimes?

OMG，此查询使mysql服务器停机.很快就会回复你们人民:(

OMG , this query makes mysql server down. Will get back to you peoples in a second :(

所有建议对这些索引编制索引的人都是正确的. 是的，我写的查询很傻而且有错误.感谢纠正我.

All peoples those suggested Indexing the columns are all Correct. Yeh the query i wrote was silly and buggy. Thanks correcting me.

答

还考虑为您的表建立索引.我们正在100万以上的记录表上运行多个左联接，这些联接不需要一两秒钟就能返回结果.

Consider also indexing your tables. We're running multiple left joins on a 1million+ record table that doesn't take more than a second or two to return results.

使用Left Join的MySQL查询太慢

相关推荐