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44 lines
1.1 KiB
HTML
44 lines
1.1 KiB
HTML
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<p>表: <code>Person</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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| id | int |
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| email | varchar |
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+-------------+---------+
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id是该表的主键列。
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该表的每一行包含一封电子邮件。电子邮件将不包含大写字母。
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</pre>
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<p> </p>
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<p>编写一个SQL查询来 <strong>删除</strong> 所有重复的电子邮件，只保留一个id最小的唯一电子邮件。</p>
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<p>以 <strong>任意顺序</strong> 返回结果表。</p>
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<p>查询结果格式如下所示。</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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Person 表:
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+----+------------------+
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| id | email |
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+----+------------------+
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| 1 | john@example.com |
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| 2 | bob@example.com |
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| 3 | john@example.com |
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+----+------------------+
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<strong>输出:</strong>
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+----+------------------+
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| id | email |
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+----+------------------+
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| 1 | john@example.com |
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| 2 | bob@example.com |
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+----+------------------+
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<strong>解释:</strong> john@example.com重复两次。我们保留最小的Id = 1。</pre>
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