题解 | #平均活跃天数和月活人数#

# 第一步求出MAU和总活跃人数 不计天数重复
select date_format(start_time,"%Y%m") as month,round(count(distinct uid,date_format(start_time,"%Y%m%d"))/count(distinct uid),2),count(distinct uid)

from exam_record
where score is not null and year(start_time)=2021
group by month