SQL-Duplicate Emails

思路：

两种思路，可以给当成两个表也可以给当成一张表来做

group by就是按照某个属性给表分个组

way 1:

select a.Email 
from Person as a,Person as b
where a.Id <> b.Id and a.Email = b.Email

way 2:

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

SQL-Duplicate Emails

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