Many data warehouses are used in a fairly formulaic style, known as a star schema (also known as dimensional modeling [55]). The example schema in Figure 3-9 shows a data warehouse that might be found at a grocery retailer. At the center of the schema is a so-called fact table (in this example, it is called fact_sales). Each row of the fact table represents an event that occurred at a particular time (here, each row represents a customer’s purchase of a product).
