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Star Schema
A relational database schema organized around a central fact table joined to a few smaller dimension tables using foreign key references. The fact table contains raw numeric items that represent relevant business facts like price, discount values, number of units sold, dollar value, etc. The facts are typically additive and are accessed via dimensions. Since the fact tables are presummarized and aggregated along business dimensions, these tables tend to be very large. The basic premise of star schemas is that information can be classified into two groups: facts and dimensions. Facts are the core data element being analyzed. For example, units of individual items sold are facts, while dimensions are attributes about the facts. Dimensions are the product types purchased and the date of purchase. The star schema has also been called a star-join schema, data cube, data list, grid file, and multidimensional schema. The name star schema comes from the pattern formed by the entities and relationships when they are represented as an entity-relationship diagram (ERD). The results of a business activity are at the center of the star surrounded by the people, places, and things that come together to perform this activity. These dimensions are the points of the star. |