What is the main problem with this implementation SELECT f.food_id FROM Foods f JOIN Expirations e ON f.id = e.food_id WHERE e.is_expired = 1; - Using `JOIN` instead of `WHERE EXISTS` to check for record existence. - No index on the e.is_expired field - JOIN keys are not indexed - The Expirations table is redundant - The query is not protected within a transaction.

The main issue with this implementation is the use of JOIN instead of WHERE EXISTS to check for the presence of records.

JOIN combines tables and returns rows, which can lead to data duplication if there are multiple expiration records for a single food_id in the Expirations table. In contrast, WHERE EXISTS simply checks for the existence of at least one matching record, which is more efficient and prevents redundant data.

Additionally, the absence of an index on the e.is_expired field can slow down filtering, but this is secondary compared to the choice of query structure.

A more correct example of the query:

SELECT f.food_id
FROM Foods f
WHERE EXISTS (
    SELECT 1 FROM Expirations e
    WHERE e.food_id = f.id AND e.is_expired = 1
);