--第三种方法：先去重，再聚合
select t.department_name depname,
t.department_key,
listagg(t.class_key, ',') within group(order by t.class_key) as class_keys
from (select distinct s.class_key, s.department_key, s.department_name
from V_YDXG_TEACHER_KNSRDGL s) t
group by t.department_key, t.department_name
--或者
select s.department_key,
s.department_name,
listagg(s.class_key, ',') within group(order by s.class_key) as class_keys
from (select t.department_key,
t.department_name,
t.class_key,
row_number() over(partition by t.department_key, t.department_name, t.class_key order by t.department_key, t.department_name) as rn
from V_YDXG_TEACHER_KNSRDGL t
order by t.department_key, t.department_name, t.class_key) s
where rn = 1
group by s.department_key, s.department_name;