请大神看下这个语句语法改成什么样才没有问题
SELECT qu.id, qu.belong, qu.type, qu.title, qu.flag,
(SELECT wm_concat(as_num || '-' || as_info)
FROM QUESTION_ANSWER quas
WHERE quas.qu_id = qu.qu_id
order by quas.as_sort asc ) AS qu_answers
FROM QUESTION qu;
我用来做视图用的，使用wm_concat连接子表所有字段并排序，加了排序order by quas.as_sort asc后报ORA-00907: 缺失右括号，不加order by quas.as_sort asc这句的话正常~
* ORA-00907: 缺失右括号
* 00907. 00000 - "missing right parenthesis"
* *Cause:
* *Action:
请问怎么修改
