select CI_ID, wm_concat(stu_name) STU_NAME
from
(select stu.stu_id, stu.stu_name, ci.ci_id
from pm_ci ci, pm_stu stu
where instr(ci.stu_ids, stu.stu_id)>0)
group by CI_ID
select a.ci_id,
listagg(b.stu_name,',') within group(order by b.stu_id) stu_name
from pm_ci a, pm_stu b
where instr(a.stu_ids,b.stu_id) > 0
group by a.ci_id;
