Fact table

Fact tables provide the (usually) additive values that act as independent variables by which dimensional attributes are analyzed.

Each record in this fact table is therefore uniquely defined by a day, product, and store.

These "affiliate dimensions" allow for additional slices of the independent facts but generally provide insights at a higher level of aggregation (a region contains many stores).

One good design rule[1] is to never store percentages or ratios in fact tables but only calculate these in the data access tool.

The factless fact tables may be used for modeling many-to-many relationships or for capturing timestamps of events.