A,B两表
select A.ID,(select Name from B where A.BID = B.ID) as BName from Aselect A.ID,B.Name as BName from A a left join B b on a.BID = b.ID
这两句那个好一点,并且请解释下 ^__^
select A.ID,(select Name from B where A.BID = B.ID) as BName from Aselect A.ID,B.Name as BName from A a left join B b on a.BID = b.ID
这两句那个好一点,并且请解释下 ^__^
SET STATISTICS IO ON
select A.ID,(select Name from B where A.BID = B.ID) as BName from Aselect A.ID,B.Name as BName from A a left join B b on a.BID = b.ID--在消息中看哪句的表扫描次数和逻辑读次数大
在select 子句里用 子查询产生列,不是个好主意.(相当于循环中再加一个子循环)