数据库每日一题 --- 第 6 天：删除重复的电子邮箱

+-------------+---------+| Column Name | Type    |+-------------+---------+| id          | int     || email       | varchar |+-------------+---------+id是该表的主键列。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。

输入: Person 表:+----+------------------+| id | email            |+----+------------------+| 1  | john@example.com || 2  | bob@example.com  || 3  | john@example.com |+----+------------------+输出: +----+------------------+| id | email            |+----+------------------+| 1  | john@example.com || 2  | bob@example.com  |+----+------------------+解释: john@example.com重复两次。我们保留最小的Id = 1。

1.delete删除、自连接2.建议用时10~25min

delete p1from Person p1,Person p2where p1.email=p2.email and p1.id>p2.id