sql 查出一张表中重复的全部记录数据

一、在面试的时候碰到一个 问题，就是让写一张表中有id和name 两个字段，查询出name重复的全部数据，如今列下：

select * from xi a where (a.username) in  (select username from xi group by username  having count(*) > 1)

二、查询出全部数据进行分组以后，和重复数据的重复次数的查询数据，先列下：

select  count(username) as '重复次数',username from xi group by username  having count(*)>1 order by username desc

三、一下为 查看别人的 结果，现列下：查询及删除重复记录的方法大全

一、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)

二、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)

另外，MySQL中使用上面的SQL会报错：You can't specify target table 'XXX' for update in FROM clause,不能在修改表的同时去查询同一张表，所以能够像下面的语句同样，将查询结果命名为一张临时表来做为修改表数据的条件，以规避上述错误。

delete from user where user_id in(
    (select user_id from 
        (select c.* from cab_user c where c.extra_id in 
            (select  a.extra_id  from user a group  by  a.extra_id having  count(a.extra_id) > 1) and c.user_id not in 
            (select min(b.user_id) from  user b group by b.extra_id having count(b.extra_id )>1)
        ) d
    )
)

三、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)

四、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)

五、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)

(二)
比方说
在A表中存在一个字段“name”，
并且不一样记录之间的“name”值有可能会相同，
如今就是须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

若是还查性别也相同大则以下:

Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1

(三)
方法一declare @max integer,@id integerdeclare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having count(*) >； 1open cur_rowsfetch cur_rows into @id,@maxwhile @@fetch_status=0beginselect @max = @max -1set rowcount @maxdelete from 表名 where 主字段 = @idfetch cur_rows into @id,@maxendclose cur_rowsset rowcount 0

方法二＂重复记录＂有两个意义上的重复记录，一是彻底重复的记录，也即全部字段均重复的记录，二是部分关键字段重复的记录，好比Name字段重复，而其余字段不必定重复或都重复能够忽略。

　　一、对于第一种重复，比较容易解决，使用select distinct * from tableName　　就能够获得无重复记录的结果集。　　若是该表须要删除重复的记录（重复记录保留1条），能够按如下方法删除select distinct * into #Tmp from tableNamedrop table tableNameselect * into tableName from #Tmpdrop table #Tmp　　发生这种重复的缘由是表设计不周产生的，增长惟一索引列便可解决。

　　二、这类重复问题一般要求保留重复记录中的第一条记录，操做方法以下　　假设有重复的字段为Name,Address，要求获得这两个字段惟一的结果集select identity(int,1,1) as autoID, * into #Tmp from tableNameselect min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoIDselect * from #Tmp where autoID in(select autoID from #tmp2)　　最后一个select即获得了Name，Address不重复的结果集（但多了一个autoID字段，实际写时能够写在select子句中省去此列）

(四)
查询重复

select * from tablename where id in (select id from tablenamegroup by idhaving count(id) > 1)

文章转自：http://blog.csdn.net/a1108501...