Wednesday, October 31, 2012

Data Warehouse: Star Schema

Star Schema
In Data Warehouse, the combination of facts and dimensions is sometimes called a star schema.

The star schema (also called star-join schemadata cube, or multi-dimensional schema) is the simplest style of data warehouse schema. The star schema consists of one or more fact tables referencing any number of dimension tables.

Model (refer the graphic above)

  • The fact table holds the metric values recorded for a specific event. Because of the desire to hold atomic level data, there generally are a very large number of records (billions). Special care is taken to minimize the number and size of attributes in order to constrain the overall table size and maintain performance. Fact tables generally come in 3 flavors - transaction (facts about a specific event e.g. Sale), snapshot (facts recorded at a point in time e.g. Account details at month end), and accumulating snapshot tables (e.g. month-to-date sales for a product).
  • Dimension tables usually have few records compared to fact tables, but may have a very large number of attributes that describe the fact data.

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albina N muro said...

The star schema architecture is the simplest data warehouse schema. It is called a star schema because the diagram resembles a star. survival warehouse reviews

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