数据如下:a 1
b 2
c 3
c 4
d 5
e 6
e 7
e 8
f 9
....如何取
a 1
b 2
c 3
d 5
e 6
f 9
...
b 2
c 3
c 4
d 5
e 6
e 7
e 8
f 9
....如何取
a 1
b 2
c 3
d 5
e 6
f 9
...
解决方案 »
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- select * from a,b
- 这两个sql为什么
min(col2)col2
from tb
group by col1
from tb t
where not exists
(
select 1 from tb where t.列1=列1 and t.列2>列2
)
--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)
*/
group by col_a;
-- Author :fredrickhu(我是小F,向高手学习)
-- Date :2009-12-08 15:52:04
-- Version:
-- Microsoft SQL Server 2005 - 9.00.4035.00 (Intel X86)
-- Nov 24 2008 13:01:59
-- Copyright (c) 1988-2005 Microsoft Corporation
-- Developer Edition on Windows NT 5.2 (Build 3790: Service Pack 1)
--
----------------------------------------------------------------
--> 测试数据:[tb]
if object_id('[tb]') is not null drop table [tb]
go
create table [tb]([col1] varchar(1),[col2] int)
insert [tb]
select 'a',1 union all
select 'b',2 union all
select 'c',3 union all
select 'c',4 union all
select 'd',5 union all
select 'e',6 union all
select 'e',7 union all
select 'e',8 union all
select 'f',9
--------------开始查询--------------------------
select * from tb t where col2=(select min(col2) from tb where col1=t.col1)
select col1,min(col2) from tb group by col1
----------------结果----------------------------
/* col1 col2
---- -----------
a 1
b 2
c 3
d 5
e 6
f 9(6 行受影响)*/
select * from tb t where not exists(select 1 from tb where col1=t.col1 and col2>t.col2)
if object_id('ta') is not null drop table ta
create table ta ( id char(2),_id int)
insert into ta
select 'a', 1 union all
select 'b', 2 union all
select 'c', 3 union all
select 'c', 4 union all
select 'd', 5 union all
select 'e', 6 union all
select 'e', 7 union all
select 'e', 8 union all
select 'f', 9 --------sqlstatement
select id,min(_id) _id from ta group by id/*--------result----
id _id
a 1
b 2
c 3
d 5
e 6
f 9
*/
insert into lin1208 select 'a',1
union all select 'b',2
union all select 'c',2
union all select 'c',3
select distinct name,id=(select min(id) from lin1208 t1 where t0.name=t1.name) from lin1208 t0
go
drop table lin1208
2> go
id _id
-- -----------
a 1
b 2
c 3
c 4
d 5
e 6
e 7
e 8
f 9(9 rows affected)
1> select * from ta a where not exists (select 1 from ta where id=a.id and _id<a
._id);
2> go
id _id
-- -----------
a 1
b 2
c 3
d 5
e 6
f 9(6 rows affected)
1>