解析顺序

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并不按指令顺寻解析

解析优化

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ex. select * from account where name = ' '

select * from account where 1 = 1 // 优化器会把where后面的判断条件给删掉

ex2.InnerJoin和子查询一样

子查询: explain select * from account t where t.id in (select t2.id from account t2)

解析后就变成了inner join