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题解 | #牛客直播各科目出勤率#

1.思路比较清晰，分别利用两张表，一张表用来统计各科的报名人数，另一张表用来统计各科的出勤人数 with a as( select course_id,count(distinct user_id) as nums from (select user_id,course_id, (case when...

Mysql

2022-03-01

1 399

题解 | #牛客直播各科目同时在线人数#

select ct.course_id,course_name,max(dt) from (select user_id,course_id, sum(diff) over(partition by course_id order by dt) as dt from (select user_id,...

Mysql

2022-02-27

1 370

题解 | #牛客直播开始时各直播间在线人数#

select ct.course_id,ct.course_name, sum(if (SUBSTRING(in_datetime,12,5)<=SUBSTRING(course_datetime,11,5),1,0)) from attend_tb as at inner join cour...

Mysql

2022-02-27

2 548