Write a SQL query to find all duplicate emails in a table named Person.
+----+---------+ | Id | Email | +----+---------+ | 1 | a@b.com | | 2 | c@d.com | | 3 | a@b.com | +----+---------+
For example, your query should return the following for the above table:
+---------+ | Email | +---------+ | a@b.com | +---------+
Note: All emails are in lowercase.
分析：编写一个SQL查询从Person表中找出所有重复的邮箱地址。
解法一：（self join）
# Write your MySQL query statement below select distinct a.Email from Person a, Person b where a.Email=b.Email and a.Id<>b.Id
一开始，写的时候没注意把distinct给漏了，导致出错：
Submission Result: Wrong AnswerMore Details
解法二：
# Write your MySQL query statement below Select Email From Person GROUP BY Email Having count(Email)>1
原文：http://www.cnblogs.com/carsonzhu/p/4630352.html