【转】 SQL 删除，删除重复纪录

妖狐艹你老母 2022-04-14 02:38 196阅读 0赞

--如何按字段删除重复记录
    一张表里面以两个字段为唯一字段，当几条记录的这两个字段完全相同时，需要删除重复项，如下表
    a b c d
    1 2 3 4
    1 5 3 5
    1 2 7 9
    以a、b为唯一字段，第一条和第三条的a、b完全相同，所以，需要删除第一条记录1 2 3 4 或者第三条记录1 2 7 9
    即如下结果：
    a b c d
    1 2 3 4
    1 5 3 5
    或
    a b c d
    1 5 3 5
    1 2 7 9
    
    请问各位大侠这种sql语句怎么写
    
    
    CREATE TABLE Tb1(id int, [a] varchar(255), [b] varchar(255), [c] varchar(255), [d] varchar(255))
    INSERT Tb1(id, [a], [b], [c], [d])
               SELECT 1, '1','2','3','4'
    UNION ALL  SELECT 2, '1','5','3','5'
    UNION ALL  SELECT 3, '1','2','7','9'
    UNION ALL  SELECT 4, '1','4','7','6'
    
    delete Tb1 where [id] not in (select max([id]) from Tb1 group by a,b )
    select * from tb1
     
    drop table tb1
    
    如果要同时删除第一和第三行
    即如下结果：
    a b c d
    1 5 3 5
    
    语句如下：
    
    delete m from tb t
    inner join
    (
    select a ,b
    from tb
    group by a , b
    having count(*)>1
    )n
    on m.a = n.a and m.b = n.b 
    或
    delete * from tb as m,
    (
    select a ,b
    from tb
    group by a , b
    having count(*)>1
    )n
    where m.a = n.a and m.b = n.b 
    
    
    
    
    
    
    
    
    ------------------------------------------------------------------------------------
    在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢?谢谢!
    1、查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断
    select * from people
    where peopleId in (select  peopleId  from  people  group  by  peopleId  having  count(peopleId) > 1)
    
    2、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录
    delete from people 
    where peopleId  in (select  peopleId  from people  group  by  peopleId   having  count(peopleId) > 1)
    and rowid not in (select min(rowid) from  people  group by peopleId  having count(peopleId )>1)
    
    3、查找表中多余的重复记录（多个字段） 
    select * from vitae a
    where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq  having count(*) > 1)
    
    4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录
    delete from vitae a
    where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
    and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
    
    5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录
    select * from vitae a
    where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
    and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
    
    比方说在A表中存在一个字段“name”，而且不同记录之间的“name”值有可能会相同，
    现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；
    Select Name,Count(*) From A Group By Name Having Count(*) > 1
    
    如果还查性别也相同大则如下:
    Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1
    ------------------------------------------------------------------------------------------------
    declare @max integer,@id integer
    declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having count(*) >； 1
    open cur_rows
    fetch cur_rows into @id,@max
    while @@fetch_status=0
    begin
    select @max = @max -1
    set rowcount @max
    delete from 表名 where 主字段 = @id
    fetch cur_rows into @id,@max
    end
    close cur_rows
    set rowcount 0
    
    方法二
    　　有两个意义上的重复记录，一是完全重复的记录，也即所有字段均重复的记录，二是部分关键字段重复的记录，比如Name字段重复，而其他字段不一定重复或都重复可以忽略。
    　　1、对于第一种重复，比较容易解决，使用
    select distinct * from tableName
    　　就可以得到无重复记录的结果集。
    　　如果该表需要删除重复的记录（重复记录保留1条），可以按以下方法删除
    select distinct * into #Tmp from tableName
    drop table tableName
    select * into tableName from #Tmp
    drop table #Tmp
    　　发生这种重复的原因是表设计不周产生的，增加唯一索引列即可解决。
    
    　　2、这类重复问题通常要求保留重复记录中的第一条记录，操作方法如下
    　　假设有重复的字段为Name,Address，要求得到这两个字段唯一的结果集
    select identity(int,1,1) as autoID, * into #Tmp from tableName
    select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID
    select * from #Tmp where autoID in(select autoID from #tmp2)
    　　最后一个select即得到了Name，Address不重复的结果集（但多了一个autoID字段，实际写时可以写在select子句中省去此列）
    select * from tablename where id in (
    select id from tablename 
    group by id 
    having count(id) > 1)

--18号每人去掉一条重复日程
    DELETE FROM AQSIQ_CLDRC WHERE CODE IN (
          SELECT MAX(CODE),NGRNAME FROM
          (                   
                SELECT * FROM AQSIQ_CLDRC WHERE HBDATE='2013-04-18' AND PARAM2='0' and swrc is null and xwrc is null
                 
           ) 
          GROUP BY HBDATE,NGRNAME
    )

SELECT * FROM AQSIQ_CLDRC WHERE NGRNAME IN 
                 (      --查询18号重复条数大于1的条数，取ngrname
                        SELECT NGRNAME FROM AQSIQ_CLDRC WHERE HBDATE='2013-04-18' GROUP BY NGRNAME HAVING COUNT(*)>1
                 )