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