Без использования функции
SELECT *
FROM (SELECT LTRIM(sys_connect_by_path(object_name, ';'), ';') AS pole
      FROM (SELECT object_name,
                   ROW_NUMBER() OVER(ORDER BY object_name) AS num1,
                   ROW_NUMBER() OVER(ORDER BY object_name) - 1 AS num2
            FROM user_objects
            WHERE ROWNUM < 10)
      START WITH num2 = 0
      CONNECT BY num2 = PRIOR num1
      ORDER BY LEVEL DESC)
WHERE ROWNUM = 1
Использование WMSYS. WM_CONCAT
WITH t AS
 (SELECT '1' val
  FROM dual
  UNION ALL
  SELECT '13' val
  FROM dual
  UNION ALL
  SELECT '1sd' val
  FROM dual
  UNION ALL
  SELECT '871' val
  FROM dual)
SELECT WM_CONCAT(t.val) AS val
FROM t
или
SELECT WM_CONCAT(object_name) AS val
FROM all_objects