Why Snowflake?

Snowflake Schema

Snowflaking is a form of dimensional modeling in which a dimension is normalized by moving attributes with low cardinality (few distinct values) into separate dimension tables that relate to the main dimension table by using foreign keys.

Snowflakingcan be done in case of:

• Sparsely populated attributes, where most dimension member records have a NULL value for the attribute, are moved to a sub-dimension.
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• Low cardinality attributes that are queried independently.  For example, a product dimension may contain thousands of products, but only a handful of product types.  Moving the product type attribute to its own dimension table can improve performance when the product types are queried independently.
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• Attributes that are part of a hierarchy and are queried independently.  Examples include the year, quarter, and month attributes of a date hierarchy; and the country and state attributes of a geographic hierarchy.