Star schema
The star schema (sometimes referenced as star join schema) is the simplest style of data warehouse schema. The star schema consists of a few fact tables (possibly only one, justifying the name) referencing any number of dimension tables. The star schema is considered an important special case of the snowflake schema.
Model
The facts that the data warehouse helps analyze are classified along different dimensions: the fact tables hold the main data, while the usually smaller dimension tables describe each value of a dimension and can be joined to fact tables as needed.
The facts that the data warehouse helps analyze are classified along different dimensions: the fact tables hold the main data, while the usually smaller dimension tables describe each value of a dimension and can be joined to fact tables as needed.
Snowflake schema
In the snowflake schema, however, dimensions are normalized into multiple related tables whereas the star schema's dimensions are denormalized with each dimension being represented by a single table.
The star and snowflake schema are most commonly found in dimensional data warehouses and data marts where speed of data retrieval is more important than the efficiency of data manipulations.
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