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sql如何把重复数据记录删除(sql分组后二次汇总处理表重复记录查询和删除的实现方法)

更多 时间:2022-01-21 00:34:33 类别:数据库 浏览量:2352

sql如何把重复数据记录删除

sql分组后二次汇总处理表重复记录查询和删除的实现方法

--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)