[LeetCode_SQL] 196. Delete Duplicate Emails - Oracle & MySQL

LeetCode SQL Study-Plan

 196. Delete Duplicate Emails 

Table: Person

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| id          | int     |
| email       | varchar |
+-------------+---------+
id is the primary key column for this table.
Each row of this table contains an email. The emails will not contain uppercase letters.

 

Write an SQL query to delete all the duplicate emails, keeping only one unique email with the smallest id. Note that you are supposed to write a DELETE statement and not a SELECT one.

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 query result format is in the following example.

 

Example 1:

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.

---

196. Delete Duplicate Emails

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

person 테이블의 중복되는 이메일 중에서, 제일 작은 Id 값을 제외한 나머지 로우를 삭제하는 쿼리

 

 Oracle 

DELETE FROM person p
WHERE p.id != (
              SELECT min(pp.id)
              FROM person pp
              WHERE pp.email = p.email
              );

 MySQL 

DELETE p FROM person p, person pp
WHERE p.email = pp.email 
AND p.id > pp.id;