Bringing Together Facts and Dimensions part -6

Fact vs Dimension Attribute

Ø  Fact attribute

4  The field is a measurement that takes on lots of values and participates in calculation

4  Ex) standard cost for a product is fact

§  seems like a constant attribute of the product but may be changed so often that eventually

Ø  Dimension attribute

4  The field is a discretely valued description that is more or less constant and participates in constraints

Ø  Occasionally, we can’t be certain of the classification

4  it may be possible to model the data field either way, as a matter of designer’s prerogative

Bringing Together Facts and Dimensions – Star Schema

Ø  The fact table consisting of numeric measurements is joined to a set of dimension tables filled with descriptive attributes

Ø  This characteristic star-like structure is often called a star join schema

Ø  All dimension are symmetrically equal entry points into the fact table

Ø  We Certainly don’t want to adjust our schemas if business users come up with new ways to analyze the business

Bringing Together Facts and Dimensions