SELECT
AVG(next_rental_date - return_date) AS avg_days_between_rentals
FROM (
SELECT
drive_id,
return_date,
LEAD(rental_date) OVER (PARTITION BY drive_id ORDER BY rental_date) AS next_rental_date
FROM rentals
) t
WHERE next_rental_date IS NOT NULL
;
show status like 'Last_query_cost';