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English Version

题目描述

编写一个 SQL 查询,查找 Person 表中所有重复的电子邮箱。

示例:

+----+---------+
| Id | Email   |
+----+---------+
| 1  | [email protected] |
| 2  | [email protected] |
| 3  | [email protected] |
+----+---------+

根据以上输入,你的查询应返回以下结果:

+---------+
| Email   |
+---------+
| [email protected] |
+---------+

说明:所有电子邮箱都是小写字母。

解法

SQL

SELECT Email
FROM Person
GROUP BY Email
HAVING count(Email) > 1;
SELECT DISTINCT p1.email
FROM person AS p1,
    person AS p2
WHERE p1.id != p2.id
    AND p1.email = p2.email;