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+<h2><a href="https://leetcode.com/problems/user-activity-for-the-past-30-days-i/">1141. User Activity for the Past 30 Days I</a></h2><h3>Easy</h3><hr><div class="sql-schema-wrapper__3VBi"><a class="sql-schema-link__3cEg">SQL Schema<svg viewBox="0 0 24 24" width="1em" height="1em" class="icon__1Md2"><path fill-rule="evenodd" d="M10 6L8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"></path></svg></a></div><div><p>Table: <code>Activity</code></p>
+
+<pre>+---------------+---------+
+| 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.
+</pre>
+
+<p>&nbsp;</p>
+
+<p>Write a solution to find the daily active user count for a period of <code>30</code> days ending <code>2019-07-27</code> inclusively. A user was active on someday if they made at least one activity on that day.</p>
+
+<p>Return the result table in <strong>any order</strong>.</p>
+
+<p>The&nbsp;result format is in the following example.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre><strong>Input:</strong> 
+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   |
++---------+------------+---------------+---------------+
+<strong>Output:</strong> 
++------------+--------------+ 
+| day        | active_users |
++------------+--------------+ 
+| 2019-07-20 | 2            |
+| 2019-07-21 | 2            |
++------------+--------------+ 
+<strong>Explanation:</strong> Note that we do not care about days with zero active users.
+</pre>
+</div>