요런식으로 할수 있겠네요.

with t
(a, b, c)
as
(
    select '1반', '12015', '우'  from dual union all
    select '1반', '12015', '수'  from dual union all
    select '1반', '12015', '미'  from dual union all
    select '2반', '12016', '수'  from dual union all
    select '2반', '12016', '수'  from dual union all
    select '2반', '12017', '수'  from dual union all
    select '2반', '12017', '우'  from dual
)
select
    a, b
    , case when count( case when c <> '수' then 1 end) > 0 then '미완성'
        else '완성' end
from t
group by a, b
order by 1;
 

감사합니다 !!! ㅠㅠㅠ