select * from belk_db_stg_event gg,
(
select  object_key,
       object_nm,
       object_crud,
       last_upd_ts,
      max(last_upd_ts) keep(dense_rank last order by last_upd_ts asc) over (partition by object_nm,object_key) as Last_UPD
       from belk_db_stg_event) ff
  where ff.object_key=gg. object_key
  and ff.object_nm=gg.object_nm
  and ff.last_upd=gg.last_upd_ts;

SQL> with 
  2    data as (
  3      select ename, deptno, hiredate,
  4             rank() over (partition by deptno order by hiredate desc) rk
  5      from emp
  6    )
  7  select deptno, ename, hiredate
  8  from data
  9  where rk = 1
 10  order by deptno
 11  /
    DEPTNO ENAME      HIREDATE
---------- ---------- -------------------
        10 MILLER     23/01/1982 00:00:00
        20 ADAMS      23/05/1987 00:00:00
        30 JAMES      03/12/1981 00:00:00