题解 | #平均活跃天数和月活人数#
平均活跃天数和月活人数
http://www.nowcoder.com/practice/9e2fb674b58b4f60ac765b7a37dde1b9
select date_format(submit_time, '%Y%m') as month,
round(
count(distinct uid, date_format(submit_time, '%Y%m%d')) / count(distinct uid), 2) as avg_active_days,
count(distinct uid) as mau
from exam_record
where submit_time is not null and year(submit_time) = 2021
group by month
很怪，为什么第三行还要用一次date_format函数？？
