Wednesday, December 14, 2011

Dimensional Modeling Skills Assessment

As everyone knows it's extremely hard to hire good people. It's equally as hard, if not harder to actually identify good people. I have previous posts with interview questions that dive into the details of T-SQL, SSRS, SSIS, SSAS, modeling, etc. Unfortunately many of these questions can be answered by those that have done a lot of reading and memorizing. It's my belief that the best technical interviews uncover a candidate's thought process, problem solving skills, and past experience. I recently put together a practical exam that attempts to do this. While I have only administered it once at this point I am confident that it is a good start to a practical skills assessment which I think should be part of any developer interview.

The assessment consists of business requirements, modeling requirements, an OLTP normalized, physical data model and some questions. The candidate is asked to review the requirements and data model and create a dimensional model that will serve as the basis for a data warehouse. There are also some follow-up questions.

The current version of the assessment asks for a dimensional model but has some questions that cross over into the physical world and assumes a SQL Server environment. It can probably be improved or at least made applicable to more organizations by making it more generic. However the position I created it for requires some knowledge of SQL Server so I incorporated it into the test.

Below is the problem statement and the physical OLTP data model. You can download the entire assessment here. Please e-mail me at if you'd like the answers.

You are a consultant and have been engaged by a manufacturing company to develop a business intelligence solution to help them reduce their raw material costs. Understanding the Purchase Order process which includes both purchases and receipts against those purchases is key to any potential cost reduction program.
The project’s sponsor has requested a first iteration of a Kimball-style dimensional model representing the material acquisition process. This model will be the basis of a star-schema based data warehouse.  It is your task to develop this model. 

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