题解 | #浙大不同难度题目的正确率#

select qd.difficult_level,	round(avg(if(qpd.result = 'right', 1, 0)), 4) correct_rate from 
user_profile up left join question_practice_detail qpd
on up.device_id = qpd.device_id
left join question_detail qd
on qpd.question_id = qd.question_id
where up.university = "浙江大学" and qd.difficult_level is not null
group by qd.difficult_level
ORDER BY correct_rate