Return the first names of customers who did not rented a film after the date '2005-08-23 02:06:01'.
SELECT first_name FROM customer WHERE customer_id NOT IN( SELECT customer_id FROM rental WHERE rental_date  >  '2005-08-23 02:06:01' )
'2005-08-23 02:06:01' tarihinden sonra bir film kiralamayan müşterilerin adlarını iade edin.