Listaggオーバーフロー関数の実装（Oracle SQL）

XMLの助けを少し借りれば、うまくいくかもしれません。例はHRスキーマに基づいています。

SQL> select
  2    listagg(s.department_name, ',') within group (order by null) result
  3  from departments s, departments d;
from departments s, departments d
     *
ERROR at line 3:
ORA-01489: result of string concatenation is too long


SQL>
SQL> select
  2  rtrim(xmlagg(xmlelement (e, s.department_name || ',')).extract
  3    ('//text()').getclobval(), ',') result
  4  from departments s, departments d;

RESULT
--------------------------------------------------------------------------------
Administration,Administration,Administration,Administration,Administration,Admin

SQL>