关于order by 或者 group by的优化。

标签：group where 索引 location document 优化 order

总结来说就一下几点。

1. 当类似这种的时候,select * from a where a.id = XXXX order by a.b;建立联合索引。当where是范围的时候不走索引的，即使建立了联合索引。具体情况可以用explain分析，看最后的Extra属性是否出现use filesort.

2.group by和上面类似。

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标签：group,where,索引,location,document,优化,order
From： https://www.cnblogs.com/andrewlovemeimei/p/16826235.html