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56 lines
2.2 KiB
HTML
56 lines
2.2 KiB
HTML
<p>Table: <code>Activity</code></p>
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<pre>
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+---------------+---------+
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| Column Name | Type |
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+---------------+---------+
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| user_id | int |
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| session_id | int |
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| activity_date | date |
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| activity_type | enum |
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+---------------+---------+
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There is no primary key for this table, it may have duplicate rows.
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The activity_type column is an ENUM of type ('open_session', 'end_session', 'scroll_down', 'send_message').
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The table shows the user activities for a social media website.
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Note that each session belongs to exactly one user.
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</pre>
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<p> </p>
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<p>Write an SQL query 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>
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<p>Return the result table in <strong>any order</strong>.</p>
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<p>The query result format is in the following example.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre>
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<strong>Input:</strong>
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Activity table:
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+---------+------------+---------------+---------------+
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| user_id | session_id | activity_date | activity_type |
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+---------+------------+---------------+---------------+
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| 1 | 1 | 2019-07-20 | open_session |
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| 1 | 1 | 2019-07-20 | scroll_down |
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| 1 | 1 | 2019-07-20 | end_session |
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| 2 | 4 | 2019-07-20 | open_session |
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| 2 | 4 | 2019-07-21 | send_message |
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| 2 | 4 | 2019-07-21 | end_session |
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| 3 | 2 | 2019-07-21 | open_session |
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| 3 | 2 | 2019-07-21 | send_message |
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| 3 | 2 | 2019-07-21 | end_session |
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| 4 | 3 | 2019-06-25 | open_session |
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| 4 | 3 | 2019-06-25 | end_session |
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+---------+------------+---------------+---------------+
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<strong>Output:</strong>
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+------------+--------------+
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| day | active_users |
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+------------+--------------+
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| 2019-07-20 | 2 |
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| 2019-07-21 | 2 |
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+------------+--------------+
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<strong>Explanation:</strong> Note that we do not care about days with zero active users.
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</pre>
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