存储过程查询的一个问题，可能你们也感兴趣
select
t.Title,
t.TopicId,
isnull(pic, '/images/fengmian1.jpg ') as pic
from
dbo.T_Novel_Topic t,dbo.T_Books_Order o
where
t.TopicId in(select top(1) from T_Books_Order o where o.OrderType=1 order by o.[DateTime] desc ) and
t.TopicId=o.TopicId and
status=1
目的就是 查询出一个表里 多条数据 只是时间不同，想取出一个时间是最新的那条数据
例如： booksid datetime
1 10:00:00
1 12:00:00
2 07:00:00
2 11:00:00
我只想要 1 12:00:00 和 2 11:00:00 条数据
我该怎么办 各位大神前来帮帮忙
[解决办法]
declare @t table([booksid] int,[datetime] datetime)insert @tselect 1,'10:00:00' union allselect 1,'12:00:00' union allselect 2,'07:00:00' union allselect 2,'11:00:00'select [booksid],convert(varchar(8),[datetime],108) as [datetime] from @t twhere [datetime]=(select max([datetime]) from @t where [booksid]=t.[booksid])order by 1/*booksid datetime----------- --------1 12:00:002 11:00:00*/
[解决办法]
declare @t table([booksid] int,[datetime] varchar(8))insert @tselect 1,'10:00:00' union allselect 1,'12:00:00' union allselect 2,'07:00:00' union allselect 2,'11:00:00'select * from @t a where not exists(select 1 from @t where [booksid]=a.[booksid] and [datetime]>a.[datetime])/*booksid datetime----------- --------1 12:00:002 11:00:00*/
[解决办法]
参考：
--> --> (Roy)生成測試數據 if not object_id('Tempdb..#T') is null drop table #TGoCreate table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2))Insert #Tselect 1,N'A',N'A1' union allselect 2,N'A',N'A2' union allselect 3,N'A',N'A3' union allselect 4,N'B',N'B1' union allselect 5,N'B',N'B2'Go--I、Name相同ID最小的记录(推荐用1,2,3),方法3在SQl05时，效率高于1、2方法1:Select * from #T a where not exists(select 1 from #T where Name=a.Name and ID<a.ID)方法2:select a.* from #T a join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID方法3:select * from #T a where ID=(select min(ID) from #T where Name=a.Name)方法4:select a.* from #T a join #T b on a.Name=b.Name and a.ID>=b.ID group by a.ID,a.Name,a.Memo having count(1)=1 方法5:select * from #T a group by ID,Name,Memo having ID=(select min(ID)from #T where Name=a.Name)方法6:select * from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)=0方法7:select * from #T a where ID=(select top 1 ID from #T where Name=a.name order by ID)方法8:select * from #T a where ID!>all(select ID from #T where Name=a.Name)方法9(注:ID为唯一时可用):select * from #T a where ID in(select min(ID) from #T group by Name)--SQL2005:方法10:select ID,Name,Memo from (select *,min(ID)over(partition by Name) as MinID from #T a)T where ID=MinID方法11:select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID) as MinID from #T a)T where MinID=1生成结果:/*ID Name Memo----------- ---- ----1 A A14 B B1(2 行受影响)*/--II、Name相同ID最大的记录,与min相反:方法1:Select * from #T a where not exists(select 1 from #T where Name=a.Name and ID>a.ID)方法2:select a.* from #T a join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID order by ID方法3:select * from #T a where ID=(select max(ID) from #T where Name=a.Name) order by ID方法4:select a.* from #T a join #T b on a.Name=b.Name and a.ID<=b.ID group by a.ID,a.Name,a.Memo having count(1)=1 方法5:select * from #T a group by ID,Name,Memo having ID=(select max(ID)from #T where Name=a.Name)方法6:select * from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)=0方法7:select * from #T a where ID=(select top 1 ID from #T where Name=a.name order by ID desc)方法8:select * from #T a where ID!<all(select ID from #T where Name=a.Name)方法9(注:ID为唯一时可用):select * from #T a where ID in(select max(ID) from #T group by Name)--SQL2005:方法10:select ID,Name,Memo from (select *,max(ID)over(partition by Name) as MinID from #T a)T where ID=MinID方法11:select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID desc) as MinID from #T a)T where MinID=1生成结果2:/*ID Name Memo----------- ---- ----3 A A35 B B2(2 行受影响)*/