if object_id('[InfoTable]') is not null drop table [InfoTable]
create table [InfoTable]([序号] int,[工序] int,[信息] varchar(10),[时间] datetime)
go
insert into [InfoTable]
select 1, 1, '1.2', '2012-8-1' union all
select 2, 1, '1.4', '2012-8-2' union all
select 3, 1, '1.8', '2012-8-3' union all
select 4, 1, '1.6', '2012-8-4' union all
select 5, 2, '1.2', '2012-8-5' union all
select 6, 2, '1.4', '2012-8-6' union all
select 7, 2, '2.1', '2012-8-7' union all
select 8, 3, '2.3', '2012-8-8' union all
select 9, 3, '2.8', '2012-8-9' union all
select 10, 3, '1.2', '2012-8-10' union all
select 11, 3, '1.4', '2012-8-11' union all
select 12, 3, '2.1', '2012-8-12' union all
select 13, 3, '2.3', '2012-8-13'
 
select [序号],[工序],[信息], [时间] from [InfoTable]
where [序号] in (select max(t.[序号]) '序号' from [InfoTable] t group by t.[工序])

/*
(13 行受影响)
序号          工序          信息         时间
----------- ----------- ---------- -----------------------
4           1           1.6        2012-08-04 00:00:00.000
7           2           2.1        2012-08-07 00:00:00.000
13          3           2.3        2012-08-13 00:00:00.000

(3 行受影响)
*/

------解决方案--------------------
SQL code

--1、用于查询重复处理记录(如果列没有大小关系时2000用生成自增列和临时表处理,SQL2005用row_number函数处理)

--> --> (Roy)生成測試數據
 
if not object_id('Tempdb..#T') is null
    drop table #T
Go
Create table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2))
Insert #T
select 1,N'A',N'A1' union all
select 2,N'A',N'A2' union all
select 3,N'A',N'A3' union all
select 4,N'B',N'B1' union all
select 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    A1
4           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=(sel