[AccessD] Mucking around

Max,

What you would normally have is an ETL (Extract-Transform-Load) process
that would get the data from the transactional system and load it into
the mart/warehouse. The data is usually transformed in some way. In the
dimension tables, all of the associated tables to the main dimension
are used to feed in the additional de-normalized data into the single
dimension table. If you do not do this, it is called snowflaking. And,
this causes poor performance from the mart/warehouse.

Marts/warehouses are not designed for efficient data storage. They are
designed for the most effective reporting possible. In some cases,
summarizing years of data into a few thousand records. No data entry
would ever be done to the mart/warehouse tables. They are always
loaded via the ETL processes defined as part of the overall strategy
the business wants to use for reporting.

I am also glad that I was able to explain it so that you were able to
get the concepts. It is usually difficult for "transactional" people
to get the concepts of a true star schema design. And they almost
always want to build snowflake schemas instead of true stars.

Robert

At 08:42 AM 9/28/2007, you wrote:
>Date: Fri, 28 Sep 2007 13:41:35 +0100
>From: <max.wanadoo at gmail.com>
>Subject: Re: [AccessD] Mucking around
>To: "'Access Developers discussion and problem solving'"
>         <accessd at databaseadvisors.com>
>Message-ID: <011c01c801cc$e8a717c0$8119fea9 at LTVM>
>Content-Type: text/plain;       charset="us-ascii"
>
>
>Hi Robert,
>Believe it or not,  I can actually understand it the way you described it.
>So, using your example, the sales would feed into the Fact Table and Reports
>would be run on the Fact table and pull info from the Customer Table.  Is
>this correct?
>Am I also correct in saying that this schema is highly inefficient in terms
>of data storage but highly efficient in terms of speed of reports?
>
>Ta
>
>Max