Question

I have built my own, very basic data warehouse. In it I have very simple cubes, for example:

Fact: ReviewRatingByday
Dimensions: Review, Organization, Date

In the OLTP side of my application, an Organization has a 1 to many relationship with Reviews.

Currently my data warehouse provides my Fact’s extract function with all possible combinations of the dimensions. This results in redundant combinations where a given Review is combined with an Organization, yet the Review is in fact associated with a different Organization.

How do other data warehouse systems avoid this?

Should I mirror my OLTP relationships in my Dimensions?

Answer 1

I don’t really understand your question. If some combinations of Review and Organization do not exist in the source data, then you will have no rows for them in the fact table anyway. So where is the “redundant combination”?

I think you might be asking, “how do I show users only valid combinations of Review and Organization when they select their report criteria”. If that’s correct then you have two main options:

1. Use a reporting tool that is able to present only valid combinations to the user
2. Combine Review and Organization into a single dimension that contains all valid combinations of Review and Organization (Kimball’s term for this is a mini-dimension)

If I misunderstood your question, please give some more information about exactly what your issue is, especially what you mean by “redundant combination”.