Oracle中實現刪除重複資料只保留一條

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為主鍵 a是有重複值的欄位
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是有重複值的欄位
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是有重複值的欄位，這個sql不會刪除任何資料
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作為臨時主鍵 a是有重複值的欄位
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;