题解 | 牛客直播开始时各直播间在线人数
牛客直播开始时各直播间在线人数
https://www.nowcoder.com/practice/bdd30e83d47043c99def6d9671bb6dbf
with a as (select course_id, count(*) online_num from attend_tb where right(in_datetime,8)<= '19:00:00' and right(out_datetime,8)>= '19:00:00' group by 1) select a.course_id, b.course_name, a.online_num from a left join course_tb b on a.course_id=b.course_id
