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48 lines
1.2 KiB
HTML
48 lines
1.2 KiB
HTML
<p>表： <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) 是这个表的主键。
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该表包含一个关注关系中关注者和用户的编号，其中关注者关注用户。</pre>
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<p> </p>
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<p>写出 SQL 语句，对于每一个用户，返回该用户的关注者数量。</p>
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<p>按 <code>user_id</code> 的顺序返回结果表。</p>
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<p>查询结果的格式如下示例所示。</p>
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<p> </p>
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<p><strong>示例 1：</strong></p>
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<pre>
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<strong>输入：</strong>
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Followers 表：
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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>输出：</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>解释：</strong>
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0 的关注者有 {1}
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1 的关注者有 {0}
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2 的关注者有 {0,1}</pre>
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