题解 | #浙大不同难度题目的正确率#
牛客每个人最近的登录日期(三)
http://www.nowcoder.com/practice/16d41af206cd4066a06a3a0aa585ad3d
select d.difficult_level,count(case when result="right" then q.device_id end)/count(q.device_id) as correct_rate
from question_practice_detail as q
join user_profile u
on u.device_id=q.device_id
join question_detail as d
on d.question_id=q.question_id
where university="浙江大学"
group by d.difficult_level
order by correct_rate asc
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，这个代码不商用是没问题的