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 up.device_id, university, count(question_id) as question_cnt, sum(if(`result` ="right",1, 0)) right_question_cnt from user_profile up left join question_practice_detail qpd on qpd.device_id = up.device_id and month(`date`) =8 where up.university = "复旦大学" #and month(`date`) =8在此处使用的话会将8月未答题的4321筛选掉，只保留了3214 group by up.device_id;
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