Star schema

[4] Having dimensions of only a few attributes, while simpler to maintain, results in queries with many table joins and makes the star schema less easy to use.

Fact tables generally consist of numeric values, and foreign keys to dimensional data where descriptive information is kept.

Star schemas are denormalized, meaning the typical rules of normalization applied to transactional relational databases are relaxed during star-schema design and implementation.

The non-primary key Units_Sold column of the fact table in this example represents a measure or metric that can be used in calculations and analysis.

For example, the following query answers how many TV sets have been sold, for each brand and country, in 1997:

Star schema used by example query