请问各位大牛,exists判断加select和直接用inner join哪个性能好些呢?
e哥 2017-10-18 09:45:25 请问这两种写法是第1种好?还是第2种好
1、inner join:
declare @Uid int=39500,
@Pwd nvarchar(99)='1A01CE9B1656D7DC34F7BBB1FF2BA3FA2EA1973B';
select vMember.Uid,vMember.Mb,vMember.mail,vMember.Rid,vMember.Nm from vMember
inner join Members on vMember.Uid=Members.Uid
where Members.Uid=@Uid and Members.Pwd=@Pwd
2、exists:
declare @Uid int=39500,
@Pwd nvarchar(99)='1A01CE9B1656D7DC34F7BBB1FF2BA3FA2EA1973B';
if exists(select Uid from Members where Uid=@Uid and Pwd=@Pwd)
select * from vMember where Uid=@Uid