怎么删除“表”中重复的记录？

如何删除“表”中重复的记录？？？
如何删除“表”中重复的记录？？？  

表的名称：linshidaList。

如果表linshidaList中，有好几条记录的DATime、MeterType、MeterNo、Qty、Qty01字段对应的值是一样的，那么将重复的记录删除，只保留一条。

这样的SQL语句应该怎样写？？？

[解决办法]

SQL code

--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--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)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),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    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,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    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,[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    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 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)*/ 
 
[解决办法]
SQL code
delete t from linshidaList t where exists(select 1 from linshidaList where DATime、MeterType=MeterType and MeterNo=t.MeterNo and Qty=t.QTY and Qty01=t.Qty01 and id<t.id)--这个ID是其他的随便一个字段
[解决办法]
探讨

delete t from linshidaList t where exists(select 1 from linshidaList where DATime=t.DATime and MeterType = t.MeterType and MeterNo=t.MeterNo and Qty=t.QTY and Qty01=t.Qty01)

这条语句不行的，把所有记录都删了。。。

……

[解决办法]
一、先去掉重复行：
select distinct DATime、MeterType、MeterNo、Qty、Qty01  into #aa from linshidaList

二、把原来表linshidaList 删除

三、把insert into linshidaList  
    select DATime、MeterType、MeterNo、Qty、Qty01 from #aa

[解决办法]
delete  from aa where a_id in (select a_id from aa a where a.a_id>(select MIN(a_id) from aa where a_num=a.a_num and a_name=a.a_name))
[解决办法]
select distinct * #temp from 表 --查询表,去掉重复行,将结果保存于昨日表中
delete 表  --  删除表数据                        
insert into 表 select * from #temp --再将临时表的数据复制到空表中
drop table #temp --删除临时表
[解决办法]
探讨

引用:

SQL code
delete t from linshidaList t where exists(select 1 from linshidaList where DATime、MeterType=MeterType and MeterNo=t.MeterNo and Qty=t.QTY and Qty01=t.Qty01 and id<t.id)--这个ID是……

[解决办法]
探讨

引用:

SQL code
delete t from linshidaList t where exists(select 1 from linshidaList where DATime、MeterType=MeterType and MeterNo=t.MeterNo and Qty=t.QTY and Qty01=t.Qty01 and id<t.id)--这个ID是……

[解决办法]
首先有一个自动增长的列ID：
然后执行以下SQL就可以
delete  from linshidaList where id not in (select max(id) from  linshidaList group by DATime,MeterType,MeterNo,Qty,Qty01)
[解决办法]
如果有ID字段，就是具有唯一性的字段


delect table where id not in (



 select max(id) from table group by col1,col2,col3...

)

注意：group by 子句后跟的字段就是你用来判断重复的条件，如只有col1，那么只要col1字段内容相同即表示记录相同。




实例：


---查询是否有重复的记录

select * from (select count(id) as counts,姓名,身份证号 from 档案 group by 姓名,身份证号) aa where  counts>1

---删除有重复的记录


delete 档案  where id not in (select max(id) from 档案 group by 姓名,身份证号)