Oracle中实现删除重复数据只保留一条

select * from 表 where Id in ( select Id from 表 group byId having count (Id) > 1)

DELETE from 表 WHERE (id) IN ( SELECT id FROM 表 GROUP BY id HAVING COUNT (id) > 1) 

AND ROWID NOT IN ( SELECT MIN (ROWID) FROM 表 GROUP BY id HAVING COUNT (*) > 1);

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

delete from 表 a where (a.Id,a.seq) in ( select Id,seq from 表 group by Id,seq having count (*) > 1)

and rowid not in ( select min (rowid) from 表 group by Id,seq having count (*)>1)

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

and rowid not in ( select min (rowid) from 表 group by Id,seq having count (*)>1)

--id为主键 a是有重复值的字段

begin

   for v in ( select a, min (id) id, count (*)

              from temp_a

              group by a

            having count (*) > 1) loop

    delete from temp_a t

      where t.a = v.a

        and t.id <> v.id;

    commit ;

   end loop;

end ;

--a是有重复值的字段

begin

   for v in ( select a, min (rowid) id, count (*)

              from temp_a

              group by a

            having count (*) > 1) loop

    delete from temp_a t

      where t.a = v.a

        and t.rowid <> v.id;

    commit ;

   end loop;

end ;

--a是有重复值的字段，这个sql不会删除任何数据

begin

   for v in ( select a, count (*) from temp_a group by a having count (*) > 1) loop

    delete from temp_a t

      where t.a = v.a

        and rownum <> 1;

    commit ;

   end loop;

end ;

select * from temp_a where rownum>1；

--新增v_id=rownum作为临时主键 a是有重复值的字段

alter table temp_a add v_id number(10);

update temp_a t set t.v_id = rownum;

commit ;

begin

   for v in ( select a, min (v_id) v_id, count (*)

              from temp_a

              group by a

            having count (*) > 1) loop

    delete from temp_a t

      where t.a = v.a

        and t.v_id <> v.v_id;

    commit ;

   end loop;

end ;

alter table temp_a drop column v_id;