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In Depth Information
Dimensions are the axis points, or ways to view facts. For instance, using the multidimensional cube in Figure 1-6
(and assuming it relates to Wal-Mart), you can ask
What is Wal-Mart’s sales volume for Date mm/dd/yyyy? Date is a dimension.
What is Wal-Mart’s sales volume in the Eastern Region? Region is a dimension.
Values around the cube that belong to a dimension are known as members . In Figure 1-6 , examples of members
are Eastern (under the Region dimension), Prod 2 (under Products), and Yearly (under Time). You might want to
aggregate various facts against various dimensions. Generating and obtaining a star schema is simple to do using
SQL Server Management Studio (SSMS). You can create a new database diagram by adding more tables from the
AdventureWorks database. SSMS will link related tables and form a star schema as shown in Figure 1-7 .
Figure 1-7. A star schema
Olap and star schemas are sometimes spoken of interchangeably.
In Figure 1-7 , the block in the center is the fact table and those surrounding the center block are dimensions. This
layout—a fact table in the center surrounded by the dimensions—is what makes a star schema.
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