1141. User Activity for the Past 30 Days I.sql

/*
Question 1141. User Activity for the Past 30 Days I
Link: https://leetcode.com/problems/user-activity-for-the-past-30-days-i/description/?envType=study-plan-v2&envId=top-sql-50

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.
*/

SELECT 
    activity_date AS day, --noqa: RF04
    COUNT(DISTINCT user_id) AS active_users
FROM Activity
WHERE activity_date BETWEEN DATE '2019-07-27' - INTERVAL '29 days' AND DATE '2019-07-27'
GROUP BY day