定位与删除表中重复数据

1、查询表中重复数据。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） 


elect * 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)


(二)
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




(三)
方法一


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


＂重复记录＂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）


(四)
查询重复


select * from tablename where id in (select id from tablename group by id 


having count(id) > 1）