leetcode Delete Duplicate Emails题解

最新推荐文章于 2020-07-02 10:09:17 发布

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本文介绍了一种使用SQL查询来删除数据表Person中重复电子邮件的方法，确保仅保留ID最小的记录，通过分组和子查询技巧实现数据清理。

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题目描述：

Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id.

+----+------------------+
| Id | Email            |
+----+------------------+
| 1  | john@example.com |
| 2  | bob@example.com  |
| 3  | john@example.com |
+----+------------------+
Id is the primary key column for this table.

For example, after running your query, the above Person table should have the following rows:

+----+------------------+
| Id | Email            |
+----+------------------+
| 1  | john@example.com |
| 2  | bob@example.com  |
+----+------------------+

Note:

Your output is the whole Person table after executing your sql. Use deletestatement.

中文理解：删除数据表Person中邮件重复的列，保留id最小的那一列。

解题思路：首先使用group by获取最小的id，然后delete from Person where Id not in(minId)。

代码（sql）：

delete from Person where Id not in (
    select minid
    from
    (select min(Id) as minid from Person group by Email) t1
);