I'm trying to create a database for a hotel company with multiple hotels. I'm stuck on how to reserve a room?
I started making a comment but noted that it would be too long. I'm not sure what parts of your ERD are given, and what parts you have created. Anyhow, here are some reflections
A room exists in a hotel, no? Assume your hotel H1 have 10 rooms and hotel H2 have 20 rooms. What prevents someone from booking room 11 in H1?
I don't understand your entity for availibility. If there are no bookings, nothing is availible? I would say that availibility is defined as (All dates x All rooms) - Bookings. Question is, do you need to store this somewhere, or can you derive it?