[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/

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