As an alternative, you can also use ROW_NUMBER()
which is a Window function that generates sequential number.
SELECT cp_id,
product_id,
competitor_id,
price,
date_added
FROM (
SELECT cp_id,
product_id,
competitor_id,
price,
date_added,
ROW_NUMBER() OVER (PARTITION BY competitor_id
ORDER BY date_added DESC) rn
FROM tblCompetitorPrices
WHERE product_ID = 1
) a
WHERE a.rn = 1
This query can easily be modified to return latest record for each competitor in every product.