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题解 | #插入记录(二)#
INSERT INTO exam_record_before_2021 SELECT null,uid,exam_id,start_time,submit_time,score FROM exam_record WHERE year(submit_...
Mysql
2022-06-23
0
173
题解 | #插入记录(一)#
insert into exam_record (uid,exam_id,start_time,submit_time,score) values(1001,9001,'2021-09-01 22:11:12','2021-09-01 23:01:12',90),(1002, 9002,...
Mysql
2022-06-23
0
146
题解 | #浙大不同难度题目的正确率#
select difficult_level, sum(if(result='right',1,0))/ count(q.question_id) correct_rate from user_profile u inner join question_pract...
Mysql
2022-06-22
0
196
题解 | #统计复旦用户8月练题情况#
select u.device_id,university, count(question_id) question_cnt ,sum(case when result='right' then 1 else 0 end ) right_question_cnt from user_pr...
Mysql
2022-06-22
0
175
题解 | #操作符混合运用#
select device_id,gender,age,university,gpa from user_profile where (gpa>3.5 and university='山东大学') or (gpa>3.8 and university=...
Mysql
2022-06-22
0
156
题解 | #分组过滤练习题#
select university , avg(question_cnt) avg_question_cnt ,avg(answer_cnt) avg_answer_cnt from user_profile u group by univ...
Mysql
2022-06-22
0
141
题解 | #分组计算练习题#
select gender, university , count(device_id) user_num ,avg(active_days_within_30) avg_active_day ,avg(question_cnt) avg_question_cnt from ...
Mysql
2022-06-22
0
168
题解 | #查找山东大学或者性别为男生的信息#
select device_id,gender,age,gpa from user_profile u where university='山东大学' union all select device_id,gender,age,gpa from user_profile u where ...
Mysql
2022-06-22
0
128
题解 | #统计每个用户的平均刷题数#
select university, difficult_level , round(count(q.question_id) / count(distinct q.device_id) ,4) as avg_answer_cnt from user_profile u in...
Mysql
2022-06-22
0
157
题解 | #统计每个学校各难度的用户平均刷题数#
select university , difficult_level, round(ifnull(count(q.question_id) / count(distinct u.id),0),4) avg_answer_cnt from user_profile u in...
Mysql
2022-06-22
0
126
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