2020-04-09-(03)

查找重复数据

编写一个 SQL 查询，查找 Person 表中所有重复的电子邮箱。

Screen Shot 2020-04-09 at 10.08.49 PM.png

Solution1

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

Solution2
自连接：不建议使用

Select distinct a.Email
From Person a join Person b
on a.Email=b.Email and a.Id<>b.Id