如何去掉數據庫重復記錄並且只保留一條記錄

在n條記錄里,存在着些相同的記錄,如何能用SQL語句,刪除掉重復並保留一條呢？方法如下：

 

1、查找表中多余的重復記錄，重復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)

2、刪除表中多余的重復記錄，重復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)  

3、查找表中多余的重復記錄（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)

4、刪除表中多余的重復記錄（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)

5、查找表中多余的重復記錄（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)