In data warehousing and data marting, star schema is the simplest form of a dimensional model, with data organized into facts and dimensions. A fact is an event that is counted or measured (such as a sale or login), and a dimension contains reference information about the fact (such as date, product, or customer). A star schema is represented by surrounding each fact with its associated dimensions, and the resulting diagrams resembles a star.
The star schema consists of one or more fact tables referencing any number of dimension tables and is effective for handling simpler queries. They are optimized for querying large data sets and are used in data warehouses and data marts to support OLAP cubes, BI and analytic applications, and ad hoc queries.