Friday, October 12, 2012

Kimball Conference Lessons Learned

I recently had the distinct privilege of attending Ralph Kimball's Dimensional Modeling In Depth class, as described in this post. Learning directly from icons such as Ralph Kimball and Margy Ross has been a huge blessing and a very enjoyable experience.  One of the most eye-opening (and valuable) experiences has involved tweaking my understanding regarding concepts that I thought I understood...but found that I didn't. Some of these misunderstandings have even come out in this blog, so I'll use this post to correct some of those...

1.) Junk Dimensions - The examples of junk dimensions that I have provided included the word "junk" in the name.  Margy Ross suggests not naming it as such, which makes a lot of sense.  Encountering a table with junk in the name may cause some confusion (perhaps even concern) for an analyst who is not well-versed in dimensional modeling.

2.) Snowflake Schema - The terms portion of my website provides the following definition for a snowflake schema

Occasionally there are reasons to join one dimension table to another dimension table. A schema in which this occurs is referred to as a snowflake schema. The ERD, in this case, will show this “second layer” of dimension tables as being similar in appearance to a snowflake.

This dimensional modeling class proved to me that this definition is a bit misleading.  Joining one dimension table to another, such as the one on the terms portion of my website, is referred to as an outrigger.  A snowflake schema involves an attempt to completely denormalize a dimension.

3.) Type 3 Slowly Changing Dimension - In this post, I described Type 3 slowly changing dimensions as being a hybrid between type 1 and type 2.  In reality, this hybrid is actually referred to as a type 6 (I need to update the other post).  So, what is a type 3 slowly changing dimension?  I'll save that explanation for a future post; however, the type 3 is not the hybrid that I thought it was.

One of the advantages of attending a course like this is that you get to bounce your knowledge against some of the most brilliant minds in the industry.  In some cases they help to affirm what you already know.  In other cases they correct what you already "know"...which turns you into a stronger asset for your organization and for the industry. 

For more information on data warehousing concepts visit  For data that can be used to practice modeling and/or ETL, click on Career in Data Warehousing and then click Grow.  Also, if you need a fresh approach to marketing your data warehousing skillset, consider The Data Warehouse Portfolio.

Saturday, October 6, 2012

Kimball University

Just as a young quarterback would be thrilled to meet Peyton Manning or a young cook would jump at the chance to meet Paula Dean, I enjoyed that experience this week in the context of my vocation.  I sat at the feet of Margy Ross and Ralph Kimball.  When you mention these names amongst non-data warehousing professionals, you are often met with confused looks.  However, those in the data warehousing arena know these individuals as some of the most brilliant minds when it comes to modeling data. 

Margy Ross spent the first two days polishing our skills on some of the more basic pieces of dimensional modeling.  She is a very professional yet light-hearted lady with a true talent for teaching these concepts.  I was blessed to learn that I had a few things wrong regarding some concepts that I thought I understand.  Some of those have even come out in this blog; the corrections for which I'll save for a future post.

Ralph Kimball spent days three and four going over some advanced concepts with regards to dimensional modeling (and a bit of ETL).  He is just as light-hearted, having the ability to explain very complex data warehousing concepts with humor inserted where appropriate.  I spent a fair portion of the class laughing, and I still smile as I remember their humor.  This was not a dry class, as some would expect (for those who enjoy data warehousing, that is).  Both Margy and Ralph are brilliant minds who have the humility to (1) impart some of their knowledge to serious data warehousing students in an interesting way and (2) answer concise questions that apply to your specific organization in a one-on-one setting (assuming you can catch them after class).  Here were some of my personal highlights...

1.) Ralph signed my copy of The Data Warehouse Toolkit by writing "Brian, keep to the grain.  Ralph Kimball".

2.) I've had a design conundrum at work regarding a many-to-many problem related to this post.  I asked him about it after class and he affirmed my suggested solution.

3.) Ralph began his first class on day three by explaining the way in which a data warehouse developer will begin asking a user what needs to exist in that user's data warehouse (which does not involve asking the question in that exact way).  As a part of that conversation, Ralph made an example out of yours truly, as though I were a successful account manager looking to implement a data warehouse. Of course he was painting a fictitious scenario to make his point but it was still a cool moment.

I would highly recommend the Dimensionsal Modeling In Depth course to anybody interested in the data warehousing arena.  I'm not affiliated with the Kimball Group in any way (other than being a fan) so I will not profit by anybody taking the course.  I recommend it because it is simply that good.

Image courtesy of smokedsalmon /