Customer(ID, name, birthDate, city);
Room(number, floor, beds, roomtype, price);
Bookings(Customer, roomNumber, floor, checkInDate, checkOutDate);
	
select Customer from Bookings
   join Room on(Bookings.num = camera.roomNumber and Bookings.floor= 
   Room.floor)
        where (Bookings.Customer, Bookings.floor) not in (select number, floor from 
        Room where roomType != 'economic')
	
select b.Customer
from Bookings b join
     Room r
     on b.num = r.roomNumber and b.floor = r.floor
group by b.Customer
having min(roomType) = max(roomType) and min(roomType) = 'economic';