So far we’ve designed fact tables that have had a very characteristic structure. Each fact table typically has three to approximately 15 to 20 key columns, followed by one to potentially several dozen numeric, continuously valued, preferably additive facts. The facts can be regarded as measurements taken at the intersection of the dimension key values. From this perspective, the facts are the justification for the fact table, and the key values are simply administrative structure to identify the facts.There are, however, a number of business processes whose fact tables are sim- ilar to those we’ve been designing with one major distinction: There are no measured facts! We call these factless fact tables. In the following examples we’ll discuss both event tracking and coverage factless fact tables. We briefly introduced the factless coverage table in Chapter 2 while discussing retail promotion coverage, as well as in Chapter 5 to describe sales rep territory coverage.