select t.* from tb t where OBJECTTYPE = 0 and SUBDATE = (select min(SUBDATE) from tb where PHONENO = t.PHONENO)
select t.* from tb t where OBJECTTYPE = 0 and not exists (select 1 from tb where PHONENO = t.PHONENO and SUBDATE < t.SUBDATE)

------解决方案--------------------
SQL code
--1.
SELECT *
  FROM order_rec a
 WHERE a.OBJECTTYPE = 0 AND
       (PHONENO, SUBDATE) IN
       (SELECT PHONENO, MIN(SUBDATE) SUBDATE FROM order_rec t GROUP BY t.PHONENO);
--2.
SELECT *
  FROM order_rec a
 WHERE a.OBJECTTYPE = 0 AND
       EXISTS (SELECT 1
          FROM (SELECT PHONENO, MIN(SUBDATE) subdate FROM order_rec t GROUP BY t.PHONENO) b
         WHERE b.PHONENO = a.PHONENO AND
               b.SUBDATE = a.SUBDATE);
--3.               
SELECT *
  FROM order_rec
 WHERE gid IN
       (SELECT MIN(GID) KEEP(dense_rank FIRST ORDER BY SUBDATE) FROM order_rec GROUP BY PHONENO) AND
       OBJECTTYPE = 0;