题解 | #浙大不同难度题目的正确率#

#select
#difficult_level,
select
difficult_level,
sum(case when result ='right' then 1 else 0 end )/COUNT(result) as right_percent
from user_profile as u
inner JOIN question_practice_detail as q on u.device_id= q.device_id
inner JOIN question_detail as qd on q.question_id=qd.question_id
where university ="浙江大学" 
group by difficult_level
order by right_percent asc;