Hi everyone I have just started a course on database design and im having some troubling understanding just exactly what tables must be broken down at each DFD.

My problem is a company that has employees and a fleet of cars, the cars can be hired many times, and can be serviced many times but auctioned only once.

I had my unnormalised data as so:

Employee No
Name
Address
Department No
Department Name
Car Reg No
model
insurance group
mileage
Hire No
Hire Date
Mileage Before
Mileage After
Service No
Service Date
Service Cost
Auction No
Auction Raised

At my First Form I had the tables sepaerated into 5 different tables,

EMPLOYEES
CARS
HIRES
SERVICE
AUCTIONS

The EMPLOYEE table has a one to many relationship with CARS and HIRES
The CARS table has a one to many relationship with the HIRES table
The CARS table has a one to many relationship with the SERVICE table
The CARS table has a one to one relationship with the AUCTION table


Is this breaking it down too much?
help appreciated