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
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