leetcode:找到名字重復的郵箱名
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.
方法1:
select Email from
(select Email,count( Email) as count from Person group by Email )as P
where count !=1;
方法2
select Email from Person group by Email having count(Email) >1