196. Delete Duplicate Emails

Delete Duplicate Emails

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

delete p1
from Person p1, Person p2
where p1.Email = p2.Email and p1.Id > p2.Id
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