[LeetCode 182] Duplicate Emails

문제 바로가기

Description

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Table: Person

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| id          | int     |
| email       | varchar |
+-------------+---------+

id is the primary key (column with unique values) for this table. Each row of this table contains an email. The emails will not contain uppercase letters.

Write a solution to report all the duplicate emails. Note that it’s guaranteed that the email field is not NULL.

Return the result table in any order.

The result format is in the following example.

Example 1

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• Input:
  • Person table:

    +----+---------+
    | id | email   |
    +----+---------+
    | 1  | a@b.com |
    | 2  | c@d.com |
    | 3  | a@b.com |
    +----+---------+
    

• Output:

  +---------+
  | Email   |
  +---------+
  | a@b.com |
  +---------+
  

• Explanation: a@b.com is repeated two times.

Constraints

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Code

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내 제출

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# Write your MySQL query statement below

SELECT email As Email 
FROM Person 
GROUP BY email 
HAVING COUNT(email) >= 2;

Runtime	Memory
355 ms	0.0 B

다른 풀이

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-- # Write your MySQL query statement below
-- select p.email from Person p where  exists (select 1 from Person p1 where p1.email=p.email AND p1.id!=p.id)
select p.email 
from Person p 
group by p.email 
having count(*)>1;

Reference

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