Table: Activity
+---------------+---------+
+| Column Name | Type |
++---------------+---------+
+| user_id | int |
+| session_id | int |
+| activity_date | date |
+| activity_type | enum |
++---------------+---------+
+This table may have duplicate rows.
+The activity_type column is an ENUM (category) of type ('open_session', 'end_session', 'scroll_down', 'send_message').
+The table shows the user activities for a social media website.
+Note that each session belongs to exactly one user.
+
+
++ +
Write a solution to find the daily active user count for a period of 30 days ending 2019-07-27 inclusively. A user was active on someday if they made at least one activity on that day.
Return the result table in any order.
+ +The result format is in the following example.
+ ++
Example 1:
+ +Input: +Activity table: ++---------+------------+---------------+---------------+ +| user_id | session_id | activity_date | activity_type | ++---------+------------+---------------+---------------+ +| 1 | 1 | 2019-07-20 | open_session | +| 1 | 1 | 2019-07-20 | scroll_down | +| 1 | 1 | 2019-07-20 | end_session | +| 2 | 4 | 2019-07-20 | open_session | +| 2 | 4 | 2019-07-21 | send_message | +| 2 | 4 | 2019-07-21 | end_session | +| 3 | 2 | 2019-07-21 | open_session | +| 3 | 2 | 2019-07-21 | send_message | +| 3 | 2 | 2019-07-21 | end_session | +| 4 | 3 | 2019-06-25 | open_session | +| 4 | 3 | 2019-06-25 | end_session | ++---------+------------+---------------+---------------+ +Output: ++------------+--------------+ +| day | active_users | ++------------+--------------+ +| 2019-07-20 | 2 | +| 2019-07-21 | 2 | ++------------+--------------+ +Explanation: Note that we do not care about days with zero active users. ++