Building on the bus architecture foundation established in Chapter 5, it's time to delve into the basics of dimensional modeling. This chapter begins with an overview of fact and dimension tables, along with the fundamental activities of drilling down, drilling across, and handling time in the data warehouse. Graceful modifications to existing dimensional models are also described.
We then turn our attention to dimensional modeling Dos and Don'ts. Finally, we discuss common myths and misunderstandings about dimensional modeling.
Basics of Dimensional Modeling
This first set of articles describes the fundamental constructs of a dimensional model.
6.1 Fact Tables and Dimension Tables
Ralph Kimball, Intelligent Enterprise, Jan 1, 2003
Dimensional modeling is a design discipline that straddles the formal relational model and the engineering realities of text and number data. Compared to third normal form entity-relationship modeling, it's less rigorous (allowing the designer more discretion in organizing the tables), but more practical because it accommodates database complexity and improves performance. Dimensional modeling has an extensive portfolio of techniques for handling real-world situations.
Measurements and Context
Dimensional modeling begins by dividing the world into measurements and context. Measurements are usually numeric and taken repeatedly. Numeric measurements are facts. Facts are always surrounded by mostly textual ...