leetcode-Database-1141|查询近30天活跃用户数

原题

思路

一个很垃圾的题，注意日期范围。

代码

select day,count(*) AS active_users from (
select distinct user_id,activity_date  as day
from Activity 
where activity_date between '2019-06-28' and '2019-07-27'
group by activity_date,user_id
) C GROUP BY day order by day