[Leetcode] Duplicate Emails Duplicate Mailbox

Write a SQL query to the Find all duplicate emails in a table named Person .

+----+---------+| Id | Email   |+----+---------+| 1  | [Email protected] | | 2  | [Email protected] | | 3  | [Email protected] |+----+---------+

For example, your query should return the following for the above table:

+---------+| Email   |+---------+| [Email protected] |+---------+

Note: All emails is in lowercase.

This problem lets us ask for duplicate mailbox, then the most direct way is to use GROUP by ... Having Count (*) ... Fixed collocation to do, the code is as follows:

Solution One:

SELECT  from GROUP  by Email  having COUNT (*>1;

We can also use the internal exchange to do, with an email to two tables, and then return the different ID lines, then two different people use the same mailbox:

Solution Two:

SELECT DISTINCT  from Person P1 JOIN  on = P2. EmailWHERE<> p2. Id;

Resources:

Https://leetcode.com/discuss/53206/a-solution-using-a-group-by-and-another-one-using-a-self-join

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[Leetcode] Duplicate Emails Duplicate Mailbox