I think what they are trying to get at is that you denormalize the company information into both tables so that you do not need the CompanyID anymore, which would then make the relationship between OrderItem and Product only based on ProductID. Hence I think A and C. But honestly that whole model is just weird.

The given answer is correct. The company entity should be denormalized into both product and customer tables. Company ID is part of the customer table and you cannot just denormalize it into the product table. and for the relationship between OrderItem and Product, you cannot just reference a part of the primary key. This is not how referencing works, your relationship would be wrong, if you only use product id and a product id is repeated for two different company IDs your relationship would consider both of them as the same product.

it can have all the answers C : A new surrogate key which combines Product and Company B:Denormalized Company into product table

The Product and customer Table already contains the CompanyId Information. As long as there are no futher information in the Company Table it can be omitted. If it can be omitted there is no need for changing the relationship, because in the current situation the one to many relation already works. In my opinion it should be A + A.

the question says : "You need to create a dimensional data model that will enable the analysis of order items by date, product, and customer." Therefore, the analysis of order item by date, product and customer doesn't need the company table (it can be omitted) ! The answer is A and A

I don't understand why not the first one is C. I think we need more information but for example in power bi models you ca nnot do relationships based in two columns, you need a combined key so I think all Fabric datamodels should work the same way.

C And C

If company has no other attribute it can be omitted

B - Since company and product both are keys within the Product table B - Since, an analysis is being performed on the date, product and customers, we need to denormalize the company with either the customer or product. But, denormalizing the company with the Customer would create unnecessary redundancy, hence, we need to consider only the Product for denormalization.

Here are my two cents on what should be the right answer: 1. Dependent on ProductID col only - If you look at the question, its asking what the relationship betwen OrderItem and Product should be. The answer is simply the ProductID col as the OrderITEM table is a fact table and having ProductID as a secondary key is the best and only solutoin. 2. The Company entity (table) must be denormalized to Product table - Again, its already convenient that we have CompanyID in Product table. So its only logical that we denormalize it in Product table only.

Correct