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

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This one is little tricky problem. I tried to use subquery approach to solve this problem.

 +----+------------------+

| 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.

Solution:

DELETE FROM Person
WHERE Id NOT IN (SELECT p.id
FROM (
SELECT MIN(Id) as id
FROM Person
GROUP BY Email) as p);


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