select ( select A.name from A where A.id=B.id) as name from B
select A.name as name from B left join A on A.id=B.id
请问一下以上两个语句是否等价,查询效率哪个更高
select ( select A.name from A where A.id=B.id) as name from B
select A.name as name from B left join A on A.id=B.id
请问一下以上两个语句是否等价,查询效率哪个更高