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
https://www.nowcoder.com/practice/d8a4f7b1ded04948b5435a45f03ead8c
select
qd.difficult_level,
sum(if (qpd.result = "right", 1, 0))/count(qpd.result) as correct_rate
from
user_profile u
join question_practice_detail qpd on u.device_id = qpd.device_id
join question_detail qd on qpd.question_id = qd.question_id
where
university = "浙江大学"
group by
difficult_level
order by
correct_rate
不要用left join ，用join即可
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