【MySQL】【leetcode】 Duplicate Emails解题报告

题目

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.

题目来源：https://leetcode.com/problems/duplicate-emails/

代码

有哪些邮箱重复？把邮箱显示出来。

# Write your MySQL query statement below

select Email from Person group by Email having count(Id) > 1;

注：MySQL中having关键字是在数据分组之后进行过滤选择分组，而where是在分组之前用来选择记录。where排除的记录不再包括在分组中。