So far you have dealt with the Jigsaw puzzles database, a database used for daily operational work. In the real-world, a database like this is maintained by an On-Line Transaction Processing (OLTP) system. The users of an OLTP system perform operational tasks—sell products, process orders, control stock, and so on.
As a counterpart, a datawarehouse is a nonoperational database; it is a specialized database designed for decision support purposes. Users of a datawarehouse analyze the data, and they do it from different points of view.
The most used technique for delivering data to datawarehouse users is dimensional modeling. This technique makes databases simple and understandable.
The primary table in a dimensional model is the fact table. A fact table stores numerical measurements of the business such as quantity of products sold, amount represented by the sold products, discounts, taxes, number of invoices, number of claims, and anything that can be measured...