It seems that the structure of the database is not really coherent. Maybe I don't understand what you are trying to do, but ... anyway, here goes.
Assuming that what you want to do is store a list a of cars in a properly normalized relational database, first thing you want to do is think what is happenning in "real life":
- Manufacturers (vendors) make/sell cars
- Manufacturers (vendors) make different models of cars
- Cars have a model (and a serial number in your case)
- Models belong to a vendor (manufacturers)
Considering this, your table structure is:
Vendors
- id
- name
Models
- id
- name
- vendor ( foreign key => vendor.id )
Cars
- id
- serial_number
- model ( foreign key => model.id )
You don't need to have a reference to the vendor in the cars table becoause you have a reference to the model, which in turn has a reference to the vendor.
Whe inserting, you do it one by one, making sure that the foreign key entries already exist.
- When you insert a car object, you just need to provide the model id.
- When you insert a model object you need to provide a vendor id.
So the Honda Civic/Accord situation does not duplicate Honda. The Tables should be something like this:
Vendor
id, name
1, "Honda"
Model
id, name, vendor
1, "Civic", 1
2, "Accord", 1
Cars
id, serial_no, model
1, "A serial", 2 -> a honda accord
2, "Another serial", 1 -> a honda civic
Hope this helps somewhat.