Create user-activity-for-the-past-30-days-i.sql

Author: kamyu104

MySQL/user-activity-for-the-past-30-days-i.sql

@@ -0,0 +1,9 @@
+# Time:  O(n)
+# Space: O(n)
+
+SELECT activity_date           AS day, 
+       Count(DISTINCT user_id) AS active_users 
+FROM   activity 
+GROUP  BY activity_date 
+HAVING Datediff("2019-07-27", activity_date) < 30 
+ORDER  BY NULL