The use of secondary dimension tables, or outrigger tables, are supported although not required for a star schema. Outrigger tables can only be related to dimension tables, where the outrigger table is the parent and the dimension table is the child. The relationship between the outrigger table and the dimension table may be identifying or non-identifying. An outrigger table cannot be related to a fact table. You can use outrigger tables to normalize data in dimension tables, though most data warehouse experts recommend against normalizing data in a warehouse because it reduces the querying performance gained by a star schema.
When outrigger tables are used in a dimensional model to decompose, or normalize, dimension hierarchies for each many-to-one relationship, the model is called a snowflake schema.
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