如何去掉數據庫重複記錄而且只保留一條記錄

在n條記錄裏,存在着些相同的記錄,如何能用SQL語句,刪除掉重複並保留一條呢？方法以下：

單個字段

一、查找表中多餘的重複記錄，重複記錄是根據單個字段（peopleId）來判斷

select * from people  
where peopleId in (select  peopleId  from  people  group  by  peopleId  having  count(peopleId) > 1)

二、刪除表中多餘的重複記錄，重複記錄是根據單個字段（peopleId）來判斷，只留有rowid最小的記錄

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)

多個字段

三、查找表中多餘的重複記錄（多個字段）

select * from vitae a  
where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq  having count(*) > 1)

四、刪除表中多餘的重複記錄（多個字段），只留有rowid最小的記錄

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、查找表中多餘的重複記錄（多個字段），不包含rowid最小的記錄

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)