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55 lines
2.0 KiB
HTML
55 lines
2.0 KiB
HTML
<p>Table: <code>Logins</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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| time_stamp | datetime |
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+----------------+----------+
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(user_id, time_stamp) is the primary key (combination of columns with unique values) for this table.
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Each row contains information about the login time for the user with ID user_id.
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</pre>
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<p> </p>
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<p>Write a solution to report the <strong>latest</strong> login for all users in the year <code>2020</code>. Do <strong>not</strong> include the users who did not login in <code>2020</code>.</p>
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<p>Return the result table <strong>in any order</strong>.</p>
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<p>The result format is in the following example.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input:</strong>
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Logins table:
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+---------+---------------------+
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| user_id | time_stamp |
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+---------+---------------------+
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| 6 | 2020-06-30 15:06:07 |
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| 6 | 2021-04-21 14:06:06 |
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| 6 | 2019-03-07 00:18:15 |
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| 8 | 2020-02-01 05:10:53 |
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| 8 | 2020-12-30 00:46:50 |
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| 2 | 2020-01-16 02:49:50 |
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| 2 | 2019-08-25 07:59:08 |
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| 14 | 2019-07-14 09:00:00 |
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| 14 | 2021-01-06 11:59:59 |
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+---------+---------------------+
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<strong>Output:</strong>
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+---------+---------------------+
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| user_id | last_stamp |
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+---------+---------------------+
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| 6 | 2020-06-30 15:06:07 |
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| 8 | 2020-12-30 00:46:50 |
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| 2 | 2020-01-16 02:49:50 |
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+---------+---------------------+
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<strong>Explanation:</strong>
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User 6 logged into their account 3 times but only once in 2020, so we include this login in the result table.
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User 8 logged into their account 2 times in 2020, once in February and once in December. We include only the latest one (December) in the result table.
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User 2 logged into their account 2 times but only once in 2020, so we include this login in the result table.
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User 14 did not login in 2020, so we do not include them in the result table.
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</pre>
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