MySQL 执行计划详解
执行计划概述
MySQL 接收一条Query后,会进行SQL解析,生成语法树,接下来会生成执行计划,选择最优的执行计划进行执行,对于一条SQL,可能有多种执行计划,观察和分析执行计划可以帮助开发人员以及DBA优化SQL.
With the help of EXPLAIN, you can see where you should add indexes to tables so that the statement executes faster by using indexes to find rows. You can also use EXPLAIN to check whether the optimizer joins the tables in an optimal order