Data Warehouse Schemas

Lots of jobs require some data warehouse experience. So it is time to study up on data warehouse schemas. Here are the common ones:
  • Star
  • Snowflake
  • Fact Constellation
  • Galaxy
The star schema is the simplest. It is also the most common. It is supported by business intelligence tools. OLAP systems build cubes with them. It represents multidimensional data. In the center of the schema is a fact table, usually in the third normal form. The points of the stars are denormalized dimension tables.  It is good for simple and fast queries.

The snowflake schema is like a star schema. However the dimensional tables are normalized. The fact constellation schema has multiple fact tables. It has shared dimension tables which are large. It is more complicated. The galaxy schema has many fact tables. They have common dimensions. It is the combination of many data marts.