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题解 | #统计有未完成状态的试卷的未完成数和未完成率#

select * from (select exam_id, sum(case when submit_time is null then 1 else 0 end) as incomplete_cnt, round(sum(case whe...

2023-10-08

0 231

题解 | #每类试卷得分前3名#

select * from ( select tag as tid, uid, rank() over ( partition by ...

2023-10-04

0 180

题解 | #每个题目和每份试卷被作答的人数和次数#

(select exam_id as tid, count(distinct uid) as uv, count(*) as pv from exam_record group by exam_id) union (select question_id as tid,...

2023-10-04

0 189

题解 | #试卷发布当天作答人数和平均分#

select exam_id, count(distinct uid) as uv, round(sum(score) / count(uid), 1) as avg_score from exam_record join examination_info using...

2023-10-04

0 230

题解 | #试卷发布当天作答人数和平均分#

select exam_id, count(distinct uid) as uv, round(sum(score) / count(uid), 1) as avg_score from exam_record join examination_info using...

2023-10-04

0 228

题解 | #平均活跃天数和月活人数#

select date_format (start_time, '%Y%m') as month, round(count(distinct uid, date_format (start_time, '%Y%m%d')) / count(distinct uid), 2) as a...

2023-10-02

0 226

题解 | #得分不小于平均分的最低分#

select score as min_score_over_avg from exam_record e join examination_info using (exam_id) where tag = 'SQL' and score >= ( select avg(s...

2023-10-02

0 215

题解 | #各个视频的平均完播率#

select u.video_id, round(SUM(CASE WHEN timestampdiff(second, u.start_time, u.end_time) >= v.duration THEN 1 ELSE 0 END) / count(*), 3) as a...

2023-09-30

0 161