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题解 | #查找山东大学或者性别为男生的信息#

学会了 union all是可以不去重的！！感谢大佬 select device_id, gender, age, gpa from user_profile where university='山东大学' union all select device_id, gende...

Mysql

2022-05-24

0 299

题解 | #统计每个学校各难度的用户平均刷题数#

select u.university, qd.difficult_level, count(qpd.question_id) / count(distinct qpd.device_id) as avg_answer_cnt from question_practice_detail qpd jo...

Mysql

2022-05-23

0 570

题解 | #统计每个学校的答过题的用户的平均答题数#

select u.university, count(question_id) / count(distinct u.device_id) as avg_answer_cnt from user_profile u right join question_practice_detail q on u...

Mysql

2022-05-23

0 290