CHAPTER 7Hierarchies and Snowflakes
It is possible to describe a dimension table as a series of parent-child relationships among groups of attributes. Days make up months, months fall into quarters, and quarters fall into years, for example. This chapter explores these attribute hierarchies and their implications for the design and use of dimensional databases.
The chapter begins by developing a basic concept of what it means to drill into data. The attribute hierarchy is then introduced, and its use as a path for drilling up and down is explored. Drilling within an attribute hierarchy turns out to be one out of many ways to drill into data; several other ways to drill are described in detail.
Although a hierarchical view of drilling limits analytic ...