OLAP in practique - Oracle Express


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Stage 1 : The database structure

With the examples of the previous part, the "Best Foot Forward" database really exists on paper. To make it more interactive, we will use some product on the market. For the moment, I suggest that you use the Oracle products.

WARNING : The Oracle Express product is now outdated. The Oracle OLAP engine is included into the RDBMS 9i, 10g or 11g version. So, you will certainly not be able to get the software and to reproduce the examples, but the concepts are still valid.

It's very important to mention that I choose Oracle Express because I have used it for a long time and I know how it works. If you want to compare the various OLAP products, I suggest you to visit the sites here. Finally, all propositions for "OLAP in practice" pages with other products will be much appreciated.

To build an OLAP database in a very short time, Oracle recommends the Oracle Express Administrator tool. We will use it in this first stage to create the Best Foot Forward database.

After connecting to Oracle Express, perhaps on a different machine, the first window appears and allows you to create a new database. After entering a name and a description, we have the following:

Accueil

This first window is very reassuring, because the principal terms are familiar : dimension, variable, formula and relation. Don't hesitate to use the glossary if you're lost.

Just a little right click on "Dimension" and you're able to create all the dimensions of the database, using the following dialog box:

Dimension

The "General" tab let you define the data type (id, numeric, text, ...) of each dimension. The "Labels" tab gives you the ability to define short and long labels for each dimension, for the end user. Other options are used to optimize or manually create conjoint dimensions.

A right click on "Variable", and we can create the Quantity, TotalVTE and VAT (Value Added Tax) variables. For each one, we specify the dense and sparse dimensions.

Variable

In this example, the TotalVTE variable has a dense Time dimension, and sparse Outlet and Reference dimensions.

Finally, you guess that a right click on "Formula" allows you to create formula. Let's define the TotalVTI formula:

Formule

The equation of the formula (here : TotalVTE * TVA) is written in a specific language. I provide some examples for you in stage 4.

The database structure is now built. The main window gives us a diagram of our database.

Synthèse

Now, we have to fill this structure with data. Let's go to the next stage !


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