题解 | #浙大不同难度题目的正确率#

select
qd.difficult_level,
sum(case when q.result = 'right' then 1 else 0 end) / count(q.question_id) as correct_rate
from
question_practice_detail q
join
user_profile u
on
q.device_id = u.device_id
join
question_detail qd
on
q.question_id = qd.question_id
where
u.university = '浙江大学'
group by
qd.difficult_level
order by
correct_rate ;