A fact table typically contains at least two and possibly three kinds of elements.
- The objects that are measured (called facts) within the applicable business process are included.
- The fact table contains foreign keys to the various dimension tables in the star, which create the context for the facts. It is this combination of the foreign keys that serve as the fact table's primary key. The foreign keys also define the grain, which is a description of the finest level of detail to which a fact table goes.
- A fact table may (or may not) contain some dimension values, called degenerate dimensions. Click on a dimension table to see more information on degenerate dimensions.