Comme écrit dans la documentation
Vous devez spécifier return_date et Rental_date dans la clause select.
Il y a deux options :
SELECT DISTINCT
customer.first_name,
rental.return_date,
rental.rental_date
FROM
rental,
customer
WHERE
rental.customer_id = customer.customer_id
GROUP BY
rental.rental_id
HAVING
(
rental.return_date - rental.rental_date
) =(
...
ou
SELECT DISTINCT
customer.first_name,
(rental.return_date - rental.rental_date) as rental_duration
FROM
rental,
customer
WHERE
rental.customer_id = customer.customer_id
GROUP BY
rental.rental_id
HAVING
rental_duration =(
...
Les deux devraient fonctionner correctement.
