[SQL] 리트코드 196. Delete Duplicate Emails

문제

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 delete all duplicate emails, keeping only one unique email with the smallest id.
For SQL users, please note that you are supposed to write a DELETE statement and not a SELECT one.
For Pandas users, please note that you are supposed to modify Person in place.
After running your script, the answer shown is the Person table. The driver will first compile and run your piece of code and then show the Person table. The final order of the Person table does not matter.
The result format is in the following example.

 

https://leetcode.com/problems/delete-duplicate-emails/description/

LeetCode - The World's Leading Online Programming Learning Platform

예시

Input: 
Person table:

+----+------------------+
| id | email            |
+----+------------------+
| 1  | john@example.com |
| 2  | bob@example.com  |
| 3  | john@example.com |
+----+------------------+

Output:

+----+------------------+
| id | email            |
+----+------------------+
| 1  | john@example.com |
| 2  | bob@example.com  |
+----+------------------+

Explanation: john@example.com is repeated two times. We keep the row with the smallest Id = 1.

문제 풀이

DELETE 
FROM Person 
WHERE Id NOT IN(
    SELECT sub.min_id
    FROM(
        SELECT Email, MIN(Id) AS min_id
        FROM PERSON
        GROUP BY Email
    )sub
)

DELETE p1
FROM Person AS p1
    INNER JOIN Person AS p2 ON p1.email = p2.email
WHERE p1.id > p2.id

---

SQL을 독학하시는 분들에게 도움이 되길 바라며,

혹 더 좋은 방법이 있거나 오류가 있다면 편하게 말씀 부탁드립니다.