看看这个查询sql语句怎么写

junmasky 2011-03-11 02:37:27
表: t_1
id group uid num
1 1 u1 3
2 1 u2 5
3 1 u3 6
4 2 r1 5
5 2 r2 7
6 2 r3 8
7 3 w1 7
8 3 w2 9
9 3 w3 2
10 3 w4 1

表结构和数据如上,分组查询出每个 group中 对应uid的 num值最大的记录,查询结果如下:
id group uid num
3 1 u3 6
6 2 r3 8
8 3 w2 9

sql语句怎么写?
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快溜 2011-03-11

select *
from tb t
where not exists (select 1 from tb where group = t.group and num > t.num)

--or

select *
from tb t
where num = (select max(num) from tb where [group] = t.[group])

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michaelgong 2011-03-11


select id,t.group,uid, t.num from ( select MAX(num)as num,group from ts group by group) t
left join ts a on t.group=a.group where t.num=a.num
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--小F-- 2011-03-11
--处理表重复记录(查询和删除)
/******************************************************************************************************************************************************
1、Num、Name相同的重复值记录,没有大小关系只保留一条
2、Name相同,ID有大小关系时,保留大或小其中一个记录
整理人:中国风(Roy)

日期:2008.06.06
******************************************************************************************************************************************************/

--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=(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 A3
5 B B2

(2 行受影响)
*/



--2、删除重复记录有大小关系时,保留大或小其中一个记录


--> --> (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),保留最小一条
方法1:
delete a from #T a where exists(select 1 from #T where Name=a.Name and ID<a.ID)

方法2:
delete a from #T a left join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null

方法3:
delete a from #T a where ID not in (select min(ID) from #T where Name=a.Name)

方法4(注:ID为唯一时可用):
delete a from #T a where ID not in(select min(ID)from #T group by Name)

方法5:
delete a from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)>0

方法6:
delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID)

方法7:
delete a from #T a where ID>any(select ID from #T where Name=a.Name)



select * from #T

生成结果:
/*
ID Name Memo
----------- ---- ----
1 A A1
4 B B1

(2 行受影响)
*/


--II、Name相同ID保留最大的一条记录:

方法1:
delete a from #T a where exists(select 1 from #T where Name=a.Name and ID>a.ID)

方法2:
delete a from #T a left join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null

方法3:
delete a from #T a where ID not in (select max(ID) from #T where Name=a.Name)

方法4(注:ID为唯一时可用):
delete a from #T a where ID not in(select max(ID)from #T group by Name)

方法5:
delete a from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)>0

方法6:
delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID desc)

方法7:
delete a from #T a where ID<any(select ID from #T where Name=a.Name)


select * from #T
/*
ID Name Memo
----------- ---- ----
3 A A3
5 B B2

(2 行受影响)
*/





--3、删除重复记录没有大小关系时,处理重复值


--> --> (Roy)生成測試數據

if not object_id('Tempdb..#T') is null
drop table #T
Go
Create table #T([Num] int,[Name] nvarchar(1))
Insert #T
select 1,N'A' union all
select 1,N'A' union all
select 1,N'A' union all
select 2,N'B' union all
select 2,N'B'
Go

方法1:
if object_id('Tempdb..#') is not null
drop table #
Select distinct * into # from #T--排除重复记录结果集生成临时表#

truncate table #T--清空表

insert #T select * from # --把临时表#插入到表#T中

--查看结果
select * from #T

/*
Num Name
----------- ----
1 A
2 B

(2 行受影响)
*/

--重新执行测试数据后用方法2
方法2:

alter table #T add ID int identity--新增标识列
go
delete a from #T a where exists(select 1 from #T where Num=a.Num and Name=a.Name and ID>a.ID)--只保留一条记录
go
alter table #T drop column ID--删除标识列

--查看结果
select * from #T

/*
Num Name
----------- ----
1 A
2 B

(2 行受影响)

*/

--重新执行测试数据后用方法3
方法3:
declare Roy_Cursor cursor local for
select count(1)-1,Num,Name from #T group by Num,Name having count(1)>1
declare @con int,@Num int,@Name nvarchar(1)
open Roy_Cursor
fetch next from Roy_Cursor into @con,@Num,@Name
while @@Fetch_status=0
begin
set rowcount @con;
delete #T where Num=@Num and Name=@Name
set rowcount 0;
fetch next from Roy_Cursor into @con,@Num,@Name
end
close Roy_Cursor
deallocate Roy_Cursor

--查看结果
select * from #T
/*
Num Name
----------- ----
1 A
2 B

(2 行受影响)
*/
回复
YouAreMyLuck 2011-03-11
select tt.* from tt,(select grop,max(num) num from tt group by grop)t where tt.grop=t.grop and tt.num= t.num


注:tt=t_1 、 grop=group
回复

select *
from tb t
where num = (select max(num) from tb where [group] = t.[group])
回复

select *
from tb t
where not exists (select 1 from tb where group = t.group and num > t.num)
回复
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