how many apartments have bookings with status code "confirmed"?
SELECT count ( * )  FROM Apartment_Bookings AS T1 JOIN Apartments AS T2 ON T1.apt_id   =   T2.apt_id WHERE T1.booking_status_code   =   "Confirmed"
count of apartments with bookings = COUNT(*); booking status code 'confirmed' refers to booking_status_code = 'Confirmed'; JOIN is used to connect related tables (Apartment_Bookings and Apartments);