Fact Table

Data marts are built around a single fact table. A data mart is defined by its fact table. A fact table is created from the OLTP application data layer Instance, Detail and sometimes Journal components. Fact table attributes, which are atomic and additive and their relationships are found in business objects, such as Invoices, Claims and Bills of Lading.

The primary key of a fact table contains the foreign keys of the dimensions in the data mart. The fact table key is a compound, non-atomic key. It is the many-end of the relationship between the fact table and all of its associated dimensions. The primary key hierarchy is usually time, organizations, people then things. There may be multiples of classes. For example, a fact table may have a relationship to customers, ship tos, carriers and insurers. In such a case, there would be four Organization.Ids as part of the primary key.

Note that Order.Number is carried as an indexed attribute in the fact table, not a key. It serves as a secondary key and is used for reporting purposes.