题解 | 浙大不同难度题目的正确率
select
difficult_level,count(case when b.result='right' then 1 else null end )/count(b.question_id) correct_rate
from
user_profile a
left join question_practice_detail b on a.device_id = b.device_id
inner join question_detail c on b.question_id = c.question_id
where
a.university = '浙江大学'
group by difficult_level
order by correct_rate
