LeetCode： Duplicate Emails
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.
将自身连接，等值项为email，然后寻找id不同email相同的元组。 第一次写这种题，数据库还真难。看来还有很长的路要走。
# Write your MySQL query statement below
select distinct C.AEmail as Email
from
(select A.Id as AId,A.Email as AEmail,B.Id as BId,B.Email as BEmail
from Person as A,Person as B
where A.Email=B.Email) as C
where C.AId<>C.BId
and C.AEmail=C.BEmail;
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