国外版

算法题（国外版）/delete-duplicate-emails.html

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+<p>Table: <code>Person</code></p>
+
+<pre>
++-------------+---------+
+| Column Name | Type    |
++-------------+---------+
+| id          | int     |
+| email       | varchar |
++-------------+---------+
+id is the primary key column for this table.
+Each row of this table contains an email. The emails will not contain uppercase letters.
+</pre>
+
+<p>&nbsp;</p>
+
+<p>Write an SQL query to <strong>delete</strong> all the duplicate emails, keeping only one unique email with the smallest <code>id</code>. Note that you are supposed to write a <code>DELETE</code> statement and not a <code>SELECT</code> one.</p>
+
+<p>Return the result table in <strong>any order</strong>.</p>
+
+<p>The query result format is in the following example.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> 
+Person table:
++----+------------------+
+| id | email            |
++----+------------------+
+| 1  | john@example.com |
+| 2  | bob@example.com  |
+| 3  | john@example.com |
++----+------------------+
+<strong>Output:</strong> 
++----+------------------+
+| id | email            |
++----+------------------+
+| 1  | john@example.com |
+| 2  | bob@example.com  |
++----+------------------+
+<strong>Explanation:</strong> john@example.com is repeated two times. We keep the row with the smallest Id = 1.
+</pre>