i am doint the ERD for a car rental company. this company has got Branches all over Europe. If one branch does not have the requested vehicle, it will check its other braches all over Europe and if they do not also have the requested vehicle, it will ask a local hire rival for the requested vehicle.
i have drawn my ERD however, i am not sure it is the correct way to represent this senario. I was wondering whether it is possible to make the Branch recursive in order to describe that one branch is checking the other branch in the company.
another question is regarding to the vehicle and fleet, in my senario the company rent out both individual vehicle or fleet. I was wondering whether my erd is correct the relation between the vehicle and fleet.
Since in your described scenario, all branches are checked if the target branch cannot supply the vehicle, there is no benefit to using a recursive relationship. There are other benefits from a recursive business relationship though, so you may consider implementing one anyway.
If it's not practically useful, then it's practically useless.