Star schema
Star schema is the simplest form of data warehouse schema. A star schema consists of at
least one fact table and a number of dimension tables. These tables are relational
database tables, often stored in SQL Server. The star schema source tables are
not required to be stored in SQL Server. In fact, many OLAP solutions use other
relational database management system (RDBMS) platforms, to hold source star
data. It is called a star schema because the entity-relationship diagram
between dimensions and fact tables resembles a star where one fact table is
connected to multiple dimensions.
A star schema fact table consists of at
least two types of columns: keys and measures.
Keys are
foreign key (FK) values that relate rows in the fact table to rows in the
dimension tables. Measures
are numeric values—usually, but not always, additive—that express the business
metrics.
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