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;