196. Delete Duplicate Emails.sql

/*

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  |
+----+------------------+
Note:

Your output is the whole Person table after executing your sql. Use delete statement.

*/

# Write your MySQL query statement below

# This using DELETE
DELETE FROM Person WHERE Id NOT IN (
        SELECT TempId FROM (
            SELECT MIN(Id) AS TempId FROM Person GROUP BY Email
        )AS minId
    );

SELECT
    MIN(Id) AS Id,
    Email
FROM Person
GROUP BY Email
ORDER BY 1 ASC