写SQL语句删除Person表中所有重复的邮箱数据，重复的邮箱只保留Id最小的邮箱数据
+----+------------------+ | Id | Email | +----+------------------+ | 1 | [email protected] | | 2 | [email protected] | | 3 | [email protected] | +----+------------------+ Id is the primary key column for this table.
例如，在运行查询语句之后，上表的保留的数据结果为
+----+------------------+ | Id | Email | +----+------------------+ | 1 | [email protected] | | 2 | [email protected] | +----+------------------+
1：先分组找出所有邮箱对应的最小Id，然后用NOT IN删除多余重复的邮箱
DELETE FROM Person
WHERE Id NOT IN (SELECT * FROM (SELECT MIN(Id)
FROM Person
GROUP BY Email) AS A)2：让两个表以邮箱关联起来，然后把相同邮箱且Id大的删除掉
DELETE P1 FROM Person P1, Person P2
WHERE P1.Email=P2.Email AND P1.Id>P2.Id上面是纯WHERE操作，下面结合JOIN，效果一致（参考：https://www.cnblogs.com/grandyang/p/5371227.html）
DELETE P1 FROM Person P1 JOIN Person P2
ON P1.Email=P2.Email WHERE P1.Id>P2.Id算法题来自：https://leetcode-cn.com/problems/delete-duplicate-emails/description/