题解 | #浙大不同难度题目的正确率#
浙大不同难度题目的正确率
http://www.nowcoder.com/practice/d8a4f7b1ded04948b5435a45f03ead8c
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 ;
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