/* relative share of each film category in
- total rental revenue
- total number of rentals */
SELECT
c.name AS category,
SUM(p.amount) / SUM(SUM(p.amount)) OVER () AS relative_rental_amount,
COUNT(*) / SUM(COUNT(*)) OVER () AS relative_rentals_count
FROM rental AS r
JOIN payment AS p ON p.rental_id = r.rental_id -- each payment belongs to one rental
JOIN inventory AS i ON i.inventory_id = r.inventory_id
JOIN film_category AS fc ON fc.film_id = i.film_id
JOIN category AS c ON c.category_id = fc.category_id
GROUP BY c.name
ORDER BY relative_rental_amount DESC;