关于sqlserver筛选重复数据的sql语句

概述--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

--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)******************************************************************************************************************************************************/--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 #TGoCreate table #T([ID] int,[name] nvarchar(1),[Memo] nvarchar(2))Insert #Tselect 1,N'A',N'A1' union allselect 2,N'A2' union allselect 3,N'A3' union allselect 4,N'B',N'B1' union allselect 5,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,Memo from (select *,min(ID)over(partition by name) as MinID from #T a)T where ID=MinID方法11:select ID,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,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,max(ID)over(partition by name) as MinID from #T a)T where ID=MinID方法11:select ID,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,N'B2'Go--I、name相同ID最小的记录(推荐用1,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 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,@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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