SELECT
rental_id,
store_id,
rental_date,
return_date,
rental_duration,
date(return_date) - date(rental_date) as dif
SELECT DATEDIFF('date(return_date)', 'date(rental_date)');
FROM
rental r
JOIN
inventory i ON r.inventory_id = i.inventory_id
JOIN
film f ON i.film_id = f.film_id