SQL重复记录查询(转载)

SQL重复记录查询(转载)

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)

例二：

select * from testtable

where numeber
in (select number from people group
by number having count(number) > 1 )

可以查出testtable表中number相同的记录




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)




(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




　　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




)