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推荐整理分享sql分组后二次汇总(处理表重复记录查询和删除)的实现方法(sql语句分组汇总),希望有所帮助,仅作参考,欢迎阅读内容。
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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:..******************************************************************************************************************************************************/
--1、用于查询重复处理记录(如果列没有大小关系时用生成自增列和临时表处理,SQL用row_number函数处理)
--> --> (Roy)生成?y????br />
--I、Name相同ID最小的记录(推荐用1,2,3),方法3在SQl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)
--SQL:
方法:select ID,Name,Memo from (select *,min(ID)over(partition by Name) as MinID from #T a)T where ID=MinID
方法:
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 A 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)
--SQL:
方法:select ID,Name,Memo from (select *,max(ID)over(partition by Name) as MinID from #T a)T where ID=MinID
方法: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 A 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?y????/p>
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 A 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 A 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?y????br /> 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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