我有一张user表
主键 id
普通索引 name
有两种写法:
SELECT * from user WHERE name = '4'
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?
我有一张user表
主键 id
普通索引 name
有两种写法:
SELECT * from user WHERE name = '4'
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?