题目:
编写一个 SQL 查询,查找 Person 表中所有重复的电子邮箱。
示例:
±—±--------+
| Id | Email |
±—±--------+
| 1 | [email protected] |
| 2 | [email protected] |
| 3 | [email protected] |
±—±--------+
根据以上输入,你的查询应返回以下结果:
±--------+
| Email |
±--------+
| [email protected] |
±--------+
创建表:
Create table If Not Exists Person (Id int,Email varchar(255));
Truncate table Person;
insert into Person (Id, Email) values ('1','[email protected]');
insert into Person (Id, Email) values ('2','[email protected]');
insert into Person (Id, Email) values ('3','[email protected]');
答案
此题比较简单,寻找重复的数据即可,用group by Email分组后 数据个数大于1的就是重复的
select Email from Person group by Email having count(Email)>1;