Editing Snowflake schema (section)

{{Short description|A logical arrangement of computing tables in a multidimensional database}}
{{distinguish|Snowflake Inc.|Snowflake ID}}
{{refimprove|date=October 2012}}
[[File:Snowflake-schema.png|350px|thumb|The snowflake schema is a variation of the star schema, featuring normalization of dimension tables.]]
[[File:Snowflake schema.png|thumb|right|]]

In [[computing]], a '''snowflake schema''' or '''snowflake model''' is a [[Logical schema|logical arrangement]] of tables in a [[multidimensional database]] such that the [[Entity-relationship model|entity relationship]] diagram resembles a [[snowflake]]  shape. The snowflake schema is represented by centralized [[fact table]]s which are connected to multiple [[Dimension (data warehouse)|dimensions]]. "Snowflaking" is a method of normalizing the dimension tables in a [[star schema]]. When it is completely normalized along all the dimension tables, the resultant structure resembles a snowflake with the [[fact table]] in the middle. The principle behind snowflaking is normalization of the dimension tables by removing low cardinality attributes and forming separate tables.<ref>Paulraj Ponniah. ''Data Warehousing Fundamentals for IT Professionals.'' Wiley, 2010, pp. 29–32. {{ISBN|0470462078}}.</ref>

The snowflake schema is similar to the star schema. However, in the snowflake schema, dimensions are [[Normalization (database)|normalized]] into multiple related tables, whereas the star schema's dimensions are denormalized with each dimension represented by a single table. A complex snowflake shape emerges when the dimensions of a snowflake schema are elaborate, having multiple levels of relationships, and the child tables have multiple parent tables ("forks in the road").