max与top的效率问题
select max ( VaryDate ) from tbl_b_Projectinfo p
inner join tbl_b_sonItems s on p.SubItemID = s.SubSupeID inner join ItemPrjVaryHistory h on h.ItemPrjId = p.ProjectID and VaryType='工程完工' where s.supeid = @Supeid
与
select top 1 VaryDate from tbl_b_Projectinfo p
inner join tbl_b_sonItems s on p.SubItemID = s.SubSupeID inner join ItemPrjVaryHistory h on h.ItemPrjId = p.ProjectID and VaryType='工程完工' where s.supeid = @Supeid order by VaryDate desc 这两句sql的执行语句有一分钟的差距了
max不是select top 1 num from table order by num desc 的函数吗?为什么max比top 1的速度这么快?