Question

I am revising a legacy multi-tenant application where the shopping cart function stores multiple vendors and multiple clients in the same database. Some clients of one vendor may be clients of a different vendor. Some vendors might actually be clients of another vendor.

I currently have a table for the super-type ‘party’ with primary key party_ID, a table for the subtype ‘company’ with primary key company_ID (references party_ID) and a table for the role of ‘vendor’ with primary key vendor_ID (references company_ID). I also have a junction table, ‘client’ with a composite primary key of vendor_ID and party_ID.

My question is how should the ‘order’ table reference the vendor and client tables? My first thought is that the table should have a composite primary key of vendor_ID, client_ID and order_ID (order_ID could be auto-increment across the table or sequential per vendor_ID + client_ID)
but this seemed a bit fishy as there were three attributes making up the key…

Does anyone have any insight into this topic? Most ‘shopping carts’ only deal with a single vendor, so the order table simply lists client_ID as a foreign key.

Thanks!

Answer 1

I would start with something like this. I do admit that I still do not quite understand difference between company, vendor, and client in your question. As Catcall mentioned, in this model you are not allowed to delete Parties (People, Organizations); accounting records should be frozen — usually by capturing current customer/supplier info in order table.

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