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.question_id) correct_rate
# if函数别忘了要指定两个返回值
from
(
select
device_id,
university
from
user_profile
where
university = '浙江大学'
) as x # 子查询并不是必须的，也可以直接连接
inner join question_practice_detail qpd on x.device_id = qpd.device_id
inner join question_detail qd on qpd.question_id = qd.question_id
group by
1
order by
2 ASC
投个大点的
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