Leetcode182. 查找重复的电子邮箱

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题目来源：182. 查找重复的电子邮箱

解法1：自连接

注意用DISTINCT。

代码：

# Write your MySQL query statement below
SELECT DISTINCT p1.Email FROM Person p1,Person p2
WHERE p1.Id!=p2.Id AND p1.Email=p2.Email

结果：

解法2：GROUP BY

以Email分组，选择count(Email)>1的Email。

代码：

# Write your MySQL query statement below
SELECT Email FROM Person
GROUP BY Email HAVING count(Email)>1

结果：