题解 | #浙大不同难度题目的正确率#

select
c.difficult_level
,sum(if(a.result = 'right',1,0)) / count(1)
from question_practice_detail a
left join user_profile b
on a.device_id = b.device_id
and b.university = '浙江大学'
left join question_detail c
on a.question_id = c.question_id
where b.device_id is not null
group by 1
order by 2