In my table i have the product id, the start_date and the end_date
as primary key.
So the problem is that if i rent a book from 10-10-2007 till 20-10-2007 That is a combination that can be fill onley one time.
But the combination of the same book end the date between 10-10-2007 en 20-10-2007 can be storage.
So i have to save al the between data to my product, that way i can't rent a book twice in one period.