Где лучше хранить скидки?

SELECT 
                product.price,
                product.id, 
                product.slug, 
                discount.price,
                IFNULL(discount.price, product.price) AS price_finish
            FROM product 
            LEFT JOIN discount ON discount.id=(
                SELECT MAX(discount.id)
                FROM discount        
                WHERE discount.product_id=product.id 
                    AND discount.status=1
            )
            WHERE product.status=1
            ORDER BY price_finish DESC