题解 | #查询结果去重#
统计复旦用户8月练题情况
http://www.nowcoder.com/practice/53235096538a456b9220fce120c062b3
select u.device_id,u.university,count(q.question_id) as question_cnt, sum(if(q.result="right",1,0)) as right_question_cnt from user_profile as u left join question_practice_detail as q on u.device_id=q.device_id and month(q.date)=8 where u.university="复旦大学" group by u.device_id
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