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 device_id,university, sum(case when question_id is not null then 1 else 0 end) as question_cnt, sum(case when result = "right" then 1 else 0 end) as right_question_cnt from ( select u.device_id,university,question_id,result 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(date) = 8 or date is null) ) t1 group by device_id,university;
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