An empty star_schema object is created in which definition of facts
and dimensions can be added.
Details
To get a star database (a star_database object) we need a flat table
and a star_schema object. The definition of facts and dimensions in
the star_schema object is made from the flat table columns.
See also
Other star schema definition functions:
define_dimension(),
define_facts(),
dimension_schema(),
fact_schema()