#1141 User Activity for the Past 30 Days I

https://leetcode.com/problems/user-activity-for-the-past-30-days-i/

MS SQL Server

SELECT activity_date as day, COUNT(DISTINCT(user_id)) as active_users
FROM Activity 
WHERE activity_date BETWEEN DATEADD(dd, -30, '2019-07-28') AND '2019-07-27'
GROUP BY activity_date