DATA WAREHOUSING FUNDAMENTALS: A Comprehensive Guide for IT Professionals

11.6. FAMILIES OF STARS

When you look at a single STAR schema with its fact table and the surrounding dimension tables, you know that is not the extent of a data warehouse. Almost all data warehouses contain multiple STAR schema structures. Each STAR serves a specific purpose to track the measures stored in the fact table. When you have a collection of related STAR schemas, you may call the collection a family of STARS. Families of STARS are formed for various reasons. You may form a family by just adding aggregate fact tables and the derived dimension tables to support the aggregates. Sometimes, you may create a core fact table containing facts interesting to most users and customized fact tables for specific user groups. Many factors lead to the existence of families of STARS. First, look at the example provided in Figure 11-16.

The fact tables of the STARS in a family share dimension tables. Usually, the time dimension is shared by most of the fact tables in the group. In the above example, all the three fact tables are likely to share the time dimension. Going the other way, dimension tables from multiple STARS may share the fact table of one STAR.

Figure 11-16. Family of STARS.

If you are in a business like banking or telephone services, it makes sense to capture individual transactions as well as snapshots at specific intervals. You may then use families of STARS consisting ...