题解 | #统计复旦用户8月练题情况#
统计复旦用户8月练题情况
https://www.nowcoder.com/practice/53235096538a456b9220fce120c062b3
select distinct u.device_id, u.university,count(q.question_id) question,
count(if(q.result = 'right',1,null)) right_question_cnt -- 筛选出回答正确的次数
from user_profile u left join question_practice_detail q
on u.device_id = q.device_id
where university = '复旦大学' and (month(q.date) = 8 or isnull(month(q.date)) = 1) -- 忽略点user_profile表中复旦大学有一个是没答题的，在question_practice_detail表中的日期为null
group by u.device_id
count(if(q.result = 'right',1,null)) right_question_cnt -- 筛选出回答正确的次数
from user_profile u left join question_practice_detail q
on u.device_id = q.device_id
where university = '复旦大学' and (month(q.date) = 8 or isnull(month(q.date)) = 1) -- 忽略点user_profile表中复旦大学有一个是没答题的，在question_practice_detail表中的日期为null
group by u.device_id
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