Solution to wm_concat function error in Oracle

In Oracle, The wm_concat function reports an error. solution: the original SQL statement select t. mail_no, wm_concat (t. notice_no) as notice_no_all from ardba. arbino t group by t. the mail_no error message solves SQL select. mail_no, wm_concat (. notice_no) | max (. str) as notice_no_all from (select k. mail_no, k. notice_no, case when k. all_sum> 4000 then '... 'else null end as str from (select t. mail_no, t. notice_no, sum (vsize (t. notice_no | ',') over (partition by t. mail_no) as all_sum, sum (vsize (t. notice_no | ',') over (partition by t. mail_no order by t. notice_no) as up_sum from ardba. arbino t) kwhere (k. up_sum <= 3998 and k. all_sum & gt; 4000) or k. all_sum <= 4001) agroup by. mail_no final