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48 lines
1.2 KiB
HTML
48 lines
1.2 KiB
HTML
<p>Table: <code>Followers</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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| follower_id | int |
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+-------------+------+
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(user_id, follower_id) is the primary key for this table.
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This table contains the IDs of a user and a follower in a social media app where the follower follows the user.</pre>
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<p> </p>
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<p>Write an SQL query that will, for each user, return the number of followers.</p>
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<p>Return the result table ordered by <code>user_id</code>.</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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Followers table:
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+---------+-------------+
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| user_id | follower_id |
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+---------+-------------+
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| 0 | 1 |
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| 1 | 0 |
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| 2 | 0 |
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| 2 | 1 |
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+---------+-------------+
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<strong>Output:</strong>
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+---------+----------------+
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| user_id | followers_count|
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+---------+----------------+
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| 0 | 1 |
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| 1 | 1 |
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| 2 | 2 |
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+---------+----------------+
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<strong>Explanation:</strong>
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The followers of 0 are {1}
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The followers of 1 are {0}
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The followers of 2 are {0,1}
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</pre>
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