Mysql 普通索引的回表的问题？

Question

我有一张user表
主键 id
普通索引 name

有两种写法:

1. SELECT * from user WHERE name = '4'

2. SELECT * from user as d1 INNER JOIN (SELECT id from user WHERE name = '4') as d2 on d1.id = d2.id

请问那种写法比较高效. 为什么高效？

Answer 1

执行顺序,第一种写法快