[LeetCode]#196. Delete Duplicate Emails

Environment : MySQL

Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id.

+----+------------------+
| Id | Email            |
+----+------------------+
| 1  | john@example.com |
| 2  | bob@example.com  |
| 3  | john@example.com |
+----+------------------+
Id is the primary key column for this table.

For example, after running your query, the above Person table should have the following rows:

+----+------------------+
| Id | Email            |
+----+------------------+
| 1  | john@example.com |
| 2  | bob@example.com  |
+----+------------------+

Solution:

# Write your MySQL query statement below
DELETE p1 FROM Person p1,
     Person p2
WHERE
     p1.Email=p2.Email AND p1.Id > p2.Id

Lesson learn:

Learn MySQL code.

Reference:

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