SQL处理重复记录
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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 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) */ |
