조합할 계수가 정해져있다고 보면 아래와 같이 하면 될것 같은데요

SELECT  SUBSTR(SYS_CONNECT_BY_PATH(COL2,'-'),2) COL0
  FROM (select   1 col1,     01 col2 from dual union all
  select   1 col1,     02 col2 from dual union all
  select   2 col1,     03 col2 from dual union all
  select   2 col1,     04 col2 from dual union all
  select   2 col1,     05 col2 from dual union all
  select   3 col1,     16 col2 from dual union all
  select   3 col1,     17 col2 from dual )
 WHERE LEVEL = 3
CONNECT BY PRIOR COL1 = COL1 -1
START WITH COL1 = 1