listagg WITHIN GROUP 不能执行

select department_id,listagg(department_name, ',') WITHIN GROUP(ORDER BY department_name) department_name from T_WX_CORP_DEPARTMENT  group by department_id;

DB2数据库10.1

执行该语句时，报错：Lookup Error - DB2 Database Error: ERROR [42601] [IBM][DB2/NT64] SQL0104N  An unexpected token "department_id,listagg(department_name, ',') WITHIN" was found following "select ".  Expected tokens may include:  "".