User activity for the past 30 days i

#
# 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.
# Note: Any activity from ('open_session', 'end_session', 'scroll_down', 'send_message') will be considered valid activity for a user to be considered active on a day.
# 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.
#

# Write your MySQL query statement below

SELECT activity_date AS day, COUNT(DISTINCT user_id) AS active_users
FROM Activity
WHERE activity_date BETWEEN DATE_SUB('2019-07-27', INTERVAL 29 DAY) AND '2019-07-27'
GROUP BY activity_date;