日期:2014-05-18 浏览次数:20665 次
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 al