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Cube dimensions are first-class database objects that contain a set of unique values for identifying and categorizing data. They create a multidimensional framework for the source data, which is stored in two-dimensional tables.
Cube dimensions form the edges of a cube, and thus of the measures within the cube. Because real-world measures are typically multidimensional, a single value in a cube measure must be qualified by a member of each dimension to be meaningful. Consider a Sales measure with four dimensions: Channel, Product, Customer, and Time. A particular Sales value only has meaning when it is qualified by a specific channel, product, customer, and time period. For example, 43,613.50 is the total for Catalog sales of Portable PCs sold to Warren Systems in July 2011.
You can define dimensions that have any of these common forms:
Level-based dimensions use parent-child relationships to group members into levels. Most dimensions are level-based.
Value-based dimensions have parent-child relationships among their members, but these relationships do not form meaningful levels.
List or flat dimensions have no levels or hierarchies.
You define dimensions as User, Time, or Measure dimensions. Detail-level dimension values typically correspond to the unique keys of a fact table.
These topics provide additional information about cube dimensions: