删除部分重复的方法.doc

-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 #TGoCreate table #T(ID int,Name nvarchar(1),Memo nvarchar(2)Insert #Tselect 1,NA,NA1 union allselect 2,NA,NA2 union allselect 3,NA,NA3 union allselect 4,NB,NB1 union allselect 5,NB,NB2Go-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=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 IDall(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 IDa.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.IDa.ID)=0方法7:select * from #T a where ID=(select top 1 ID from #T where Name= order by ID desc)方法8:select * from #T a where ID! - (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,NA,NA1 union allselect 2,NA,NA2 union allselect 3,NA,NA3 union allselect 4,NB,NB1 union allselect 5,NB,NB2Go-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 IDa.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 ID0方法6:delete a from #T a where ID(select top 1 ID from #T where Name= order by ID)方法7:delete a from #T a where IDany(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 IDa.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 IDa.ID)0方法6:delete a from #T a where ID(select top 1 ID from #T where Name= order by ID desc)方法7:delete a from #T a where ID - (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,NA union allselect 1,NA union allselect 1,NA union allselect 2,NB union allselect 2,NBGo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 IDa.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_st