I need help to fix my errors in my ERD diagram. ERD is about system delivery. I got issues that i have to consider all the FKs in Items table and not null. like
What if a customer only buys gold , then how to handle the rest of PKs’ values.
i need to have the superclass and subclass concept for those items. i have to
create a superclass that is associated with items and subclasses with unique attributes.
i should have major relationships that will be associated with the superclass.
my other issue is delivery table, it needs a relationship with CUSTOMER.
Supplier shipping Item to Customer.