Dimension Design - Professional SQL Server Analysis Services 2005 with MDX - page 165

Working with the Dimension Wizard
Dimensions help you to define the structure of your cube so as to facilitate ef-
fective data analysis. Specifically, dimensions provide you with the capability of
slicing data within a cube, and these dimensions can be built from one or more
dimension tables. As you learned in Chapter 1 , your data warehouse can be
designed as a star or snowflake schema. In a star schema, dimensions are
created from single tables that are joined to a fact table. In a snowflake
schema, two or more joined dimension tables are used to create dimensions
where one of the tables is joined to the fact table. You create both of these di-
mension types in this chapter.
You also learned in Chapters 1 and 3 that each dimension contains objects
called hierarchies. In Analysis Services 2005 you have two types of hierarchies
to contend with: the attribute hierarchy, which corresponds to a single column
in a relational table, and multilevel hierarchies, which are derived from two or
more attribute hierarchies where each attribute is a level in the multi-level hier-
archy. A typical example of an attribute hierarchy would be zip code in a Dim
Geography dimension, and a typical example for a multilevel hierarchy would
be Country-State-City-Zip Code also in a Geography dimension. In everyday
discussions of multilevel hierarchies, most people leave off the "multilevel" and
just call them " hierarchies. "
For the exercises in this chapter, you use the project you designed in Chapter
2 . If you don't happen to have the project handy, you can download it from ht-
tp://www.wrox.com . If you download or not, you will still need to add the Geo-
graphy Dimension (dbo.DimGeography) to the DSV. To add this dimension to
your DSV follow the steps below.
1. Double click on the DSV named "AdventureWorksDW.dsv" in Solution
Explorer.
2. Click on the "Add/Remove Objects" icon (top left icon in the DSV
Designer) as shown in Figure 5-1 .