最高效删除重复记录的方法，使用为例rowid

DELETE FROM EMP E WHERE E.ROWID > (SELECT MIN(X.ROWID) FROM EMP X WHERE X.EMP_NO = E.EMP_NO);

     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)
　　注:rowid为Oracle自带不用该.....
　　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

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