题解 | #牛客直播各科目平均观看时长#
牛客直播各科目平均观看时长
https://www.nowcoder.com/practice/e9e7dc4c8623467793f6999cbfee9360
select
course_name,
round(avg(times),2) as avg_len
from (select
c.course_name,
TIMESTAMPDIFF(MINUTE, a.in_datetime, a.out_datetime) as times
from course_tb as c join attend_tb as a on
c.course_id = a.course_id) t group by course_name order by avg_len desc;
重点在于求两个时间的差 timestampdiff函数
投递小天才等公司7个岗位 >