题解 | #浙大不同难度题目的正确率#

SELECT c.difficult_level,
round(sum(case when b.result = "right" then 1 else 0 end)/count(b.device_id), 4)
as correct_rate
FROM
question_practice_detail as b
left join
user_profile as a
on a.device_id = b.device_id
left join
question_detail as c
on b.question_id = c.question_id
where a.university = "浙江大学"
Group by c.difficult_level
order by correct_rate