Wednesday, January 23, 2019

Star schema

Star schema is the simplest form of a dimensional model, in which data is organized into facts and dimensions. 

A fact is an event that is counted or measured, such as a sale or login. 

A dimension contains reference information about the fact, such as date, product, or customer. A star schema is diagrammed by surrounding each fact with its associated dimensions. The resulting diagram resembles a star.

Star schema are optimized for querying large data sets and are used in data warehouses and data marts to support OLAP cubes, business intelligence and analytic applications, and ad hoc queries.

  • Within the data warehouse or data mart, a dimension table is associated with a fact table by using a foreign key relationship.  
  • The dimension table has a single primary key that uniquely identifies each member record (row).  
  • The fact table contains the primary key of each associated dimension table as a foreign key.  Combined, these foreign keys form a multi-part composite primary key that uniquely identifies each member record in the fact table.  The fact table also contains one or more numeric measures.

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