Each car belongs to a category,
Each reservation is for a category of cars,
Each location is in a city,
Each reservation has a pick up and a drop off location,
Each reservation is made by a customer,
Each rental is made by a customer,
Each rental is for a certain car,
Each rental has a pick up and a drop off location.
Each rental is connected to some insurance. But is there only one insurance for each rental? No. There can be many pieces of insurance connected to a rental (insurance against vehicle damage, against personal injuries, against injuring someone else’s car, ...). I added an intermediate table called