取最新一条SQL优化

    一开始给同事的sql是第二条，但关联查询执行起来慢，同事修改了一些第一条效率明显提升！

  最终优化SQL

CREATE VIEW [dbo].[View_Item_IsLarge]
AS
    SELECT   ItemID, DLMasterChildType
    FROM    dbo.Item_IsLarge AS A
    WHERE   A.Gid IN ( SELECT TOP ( 1 )
                                Gid
                       FROM     dbo.Item_IsLarge
                       WHERE    ( ItemID = A.ItemID )
                       ORDER BY rowModifyDate DESC ) 

GO

 一开始优化的SQL

create view [dbo].[View_Item_IsLarge2]
as
select DLMasterChildType,ItemID from (
select DLMasterChildType,ItemID,ROW_NUMBER() over(partition by ItemID order by rowModifyDate desc )rn
from dbo.Item_IsLarge ) t
where rn=1
GO