DECLARE
  I INTEGER;
BEGIN
  FOR I IN 997 .. 1002 LOOP
    IF LENGTH(I) < 3 THEN
      INSERT INTO ROOM (NUM) VALUES ('1F' || LPAD(I, 3, '0'));
    ELSE
      INSERT INTO ROOM (NUM) VALUES ('1F' || TO_CHAR(I));
    END IF;
  END LOOP;
END;
/

------解决方案--------------------
SQL code
INSERT INTO room
  (num)
  select '1F'||reverse(substr(reverse('000' || rownum), 1, 4)) as num
    from system.help t1, system.help t2
   where rownum <= 1500

------解决方案--------------------
DECLARE
 I INTEGER：=1;
BEGIN
 LOOP
   INSERT INTO ROOM (NUM) VALUES ('1F' || LPAD(I, decode(length(to_char(i)),4,4,3), '0'));
   exit when i=1500;
   i:=i+1
 END LOOP;
END;