e-r model
i tried out an e-r model for the problem below.

could anyone check it and tell whether it is right or any other thing should be added to it.(see attachement)


thanks in advance....




"Cars are uniquely identified by their registration number. Other data

of interest concerning our cars includes: year of manufacture,

manufacturer and model, kilometres travelled, date last serviced (so we

can tell when a car is due to be serviced) and comments on the

condition of the car. Additionally, each car is classified into one

particular type. The types of car we have are listed below:

small manual

small automatic

medium manual

medium automatic

large manual

large automatic

commercial vehicle

We work with different service centres. Each service centre has the

capacity to service any of our cars. Service centres are identified by a

unique number. We also require details about the service centre such

as: name, address, telephone and contact person. We personally

choose a particular service centre at a given time based on a number of

factors which are not required to be stored in the system. When a

service centre is chosen, a booking is made with that centre. The

information we require about these bookings includes: car registration

number, service centre number, date in, date out, service details,

amount due and amount paid. So that I check if a car is available to

be serviced, I need to be able to view the following data about client

rental bookings for cars - car registration number, client number, date

out and date due."

my policy is, i don't answer what is obviously a homework problem unless you have made an attempt yourself, and in this case, it looks like you have

sometimes the foreign key shows in your diagram (e.g. carregno and ssno on the booking table) and sometimes it doesn't (e.g. no model foreign key in the car table) -- so straighten that out before you hand it in

expenditure is not a child table of car -- its fields should probably be part of the booking table (expenditure for getting a car serviced)

finally, the client-car relationship should be many-to-many, i.e. there's a relationship entity missing between them

hope that helps

rudy
http://r937.com/

As eveyrone seems to be doing the same thing I have written up in detail the process by which a schema should be developed, using this as an example. Hope this helps, you'll find it here:

http://dbforums.com/t909913.html