mysql 语句，球分析

[ioven]

explain select `id` from `ao_articles` where (select count(*) from `ao_articles_tags` inner join `ao_articles_relationships` on `ao_articles_tags`.`id` = `ao_articles_relationships`.`tag_id` where `ao_articles_relationships`.`cid` = `ao_articles`.`id` and `id` in (1,2,3,4,5)) >= 1 limit 10000

应该已经添加索引，为什么还会扫描全表？

[DT27]

我一直没搞明白索引。。。帮不了忙~

[huixia0010]

count(*) 是全表扫描,自己百度下一目了然~