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
http://www.nowcoder.com/practice/d8a4f7b1ded04948b5435a45f03ead8c
就三表联结，没啥好说的。。。
select c.difficult_level
,sum(if(a.result= 'right',1,0))/count(c.question_id) correct_rate
from question_practice_detail a
left join user_profile b
on a.device_id = b.device_id
left join question_detail c
on a.question_id = c.question_id
where b.university = '浙江大学'
group by c.difficult_level
order by correct_rate 
这样才显得专业
投递字节跳动等公司6个岗位