Now that we have a list of rooms, we need to create the link between the Room and Check-in records.
A reference field can be referred to as a one-to-many relationship. This is because a room may be checked in to multiple times (you might have one particular guest one day, and the next day, another might sleep in the same room after our fabulous cleaners have done their work), but for a single check-in, you can only select one room. You can only sleep in one bed at a time!
A classic example of a one-to-many relationship is between a mother and her children. A child can only have one biological mother, but a mother can have many children.
The following diagram shows the relationship needed between the Room and Check-in ...
