I have a scenario where an Order belongs to a customer, but the order also has a Referer - which can be a customer in other situation. i.e, customer A & B. In one situation, A could be a direct customer, but in another situation A could be just a referer for B, and that needs to be recorded in the Order table.
What would be the best way to design this? At the moment all I have in mind is just two relationships between Customers table and Orders table, but it doesn't seem right.
That sounds fine to me. One relationship from customer to order, and a second relationship from referer to customer. To borrow a phrase from an almond joy commercial: Some days you feel like a nut, some days you don't!