sql分组后处理表重复记录查询和删除的解决办法

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--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

代码如下：

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 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)*/

--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 #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),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 A14 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 A35 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 #TGoCreate table #T([Num] int,[Name] nvarchar(1))Insert #Tselect 1,N'A' union allselect 1,N'A' union allselect 1,N'A' union allselect 2,N'B' union allselect 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 A2 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godelete 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goalter table #T drop column ID--删除标识列

--查看结果select * from #T

/*Num Name----------- ----1 A2 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 forselect count(1)-1,Num,Name from #T group by Num,Name having count(1)>1declare @con int,@Num int,@Name nvarchar(1)open Roy_Cursorfetch next from Roy_Cursor into @con,@Num,@Namewhile @@Fetch_status=0begin set rowcount @con; delete #T where Num=@Num and Name=@Name set rowcount 0; fetch next from Roy_Cursor into @con,@Num,@Nameendclose Roy_Cursordeallocate Roy_Cursor

--查看结果select * from #T/*Num Name----------- ----1 A2 B

(2 行受影响)

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