door komma's gescheiden lijst als resultaat van select-instructie in Oracle

SELECT parent_id,
       RTRIM(XMLAGG(XMLELEMENT(e,child_id || ',')).EXTRACT('//text()'),',') AS "Children"
  FROM parentChildTable
 WHERE parent_id = 0
 GROUP BY parent_id

of

SELECT parent_id,
       LISTAGG(child_id, ',') WITHIN GROUP (ORDER BY child_id) AS "Children"
  FROM parentChildTable
 WHERE parent_id = 0
 GROUP BY parent_id