May 2007
Intermediate to advanced
432 pages
11h 43m
English
Content preview from Expert SQL Server™ 2005 Integration Services
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4.2. Dimensions: The Basics
This chapter focuses on dimension ETL, but in order to understand the full picture of dimension ETL, some dimension theory is required. The best resource is to read The Complete Guide to Dimension Modeling, Second Edition, by Ralph Kimball and Margy Ross (Wiley Publications, 2002), for a complete picture of a dimension. For the purposes of this discussion, here's a high-level summary.
The dimension itself is an organized grouping of categories and properties about a particular entity. These categories and properties are called attributes, and they form hierarchies with levels and members used to slice and query a cube or fact table.
For example, the following table shows data focusing on geography. The attributes are the Country, State/Province and City, which combine together because of their relationship to one another.
| Country | State/Province | City |
|---|---|---|
| Germany | Bavaria | Augsburg |
| Germany | Bavaria | Munich |
| Germany | Niedersachsen | Hannover |
| United States | California | Palo Alto |
| United States | California | Woodland Hills |
| United States | New York | Cheektowaga |
| United States | New York | Lake George |
Naturally, this data can be used together to create a hierarchy, which provides drill paths to data and the ability to slice and dice data based on certain records. Figure 4-1 shows one of the hierarchies within this geography dimension. The members are the names of the countries, state provinces, and cities. The hierarchy is made up of levels that usually correspond to the column names used in the hierarchy. ...
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