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题解 | #牛客直播各科目平均观看时长#

select course_name, round(avg(timestampdiff(minute, in_datetime, out_datetime)),2) as avg_Len from attend_tb join course_tb using (course_id) group...

2023-10-08

0 305

某乎问答回答过教育类问题的用户里有多少用户回答过职场类问题

select count(*) as num from answer_tb a join issue_tb using (issue_id) where issue_type = 'Career' and a.author_id in ( select author_id fro...

2023-10-08

0 323

题解 | #某乎问答单日回答问题数大于等于3个的所有用户#

select answer_date, author_id, count(*) as answer_cnt from answer_tb where month(answer_date) = 11 group by answer_date, author_id having ans...

2023-10-08

0 247

题解 | #某乎问答高质量的回答中用户属于各级别的数量#

select level_cut, count(*) as num from ( select *, case when author_level between 1 and 2 then '1-2级' when author_level between 3 and...

2023-10-08

0 364

题解 | #牛客直播开始时各直播间在线人数#

select course_id, course_name, count(distinct user_id) from attend_tb join course_tb using (course_id) where in_datetime <= substring(cou...

2023-10-08

0 265

题解 | #对过长的昵称截取处理#

select uid, if(char_length(nick_name) <= 13, nick_name, concat(substr(nick_name, 1,10),'...')) as nick_name from user_info where char_length(n...

2023-10-08

0 252

题解 | #修复串列了的记录#

select exam_id, substring_index(tag,',',1) as tag, substring_index(substring_index(tag,',',2),',',-1) as difficulty, substring_index(tag,','...

2023-10-08

0 207

题解 | #月均完成试卷数不小于3的用户爱作答的类别#

select tag, count(*) as tag_cnt from exam_record er join examination_info using (exam_id) where exists ( select uid, date_format(submit_tim...

2023-10-08

0 218

题解 | #每份试卷每月作答数和截止当月的作答总数。#

select exam_id, date_format(start_time, '%Y%m') as start_month, count(*) as month_cnt, sum(count(*)) over (partition by exam_id order by date_f...

2023-10-08

2 339

题解 | #对试卷得分做min-max归一化#

select uid, exam_id, round(avg(ifnull(((score - min_score) / (max_score - min_score)) * 100, score)),0) avg_new_score from exam_record join ex...

2023-10-08

0 301