Entity Relationship Diagram for Hotel
This looks mostly complete, though the BookingID field in Guest seems a little pessimistic. What will you do if a guest wants to stay at the hotel again in the future? As you already have a relation between Guest and Booking via GuestID, you can probably remove BookingID from Guest. A similar thing can be done in Bill as, if you know the BookingID then you know the GuestID. So GuestID can be removed from Bill … if you choose, of course. You don’t need to make either change.