如何删除数据库中重复的记录，删除后只保留唯一的一条记录

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在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢？
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)

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)