Data engineering and IT
Star schema
- Data engineering and IT
Definition
A way of organising data for analysis with one central fact table of events or measurements linked to several dimension tables that describe them.
Example
Raket Parts B.V. invoice lines (20,653 rows, the fact table) link to products (2,830 rows) and customers (436 rows), the dimension tables. Adding a date table would complete the star. A report can then filter by product family, customer segment and month in one model.
Raket Parts B.V. is a fictional company created for Insyt.
See how it works
Dimensions give context for filtering and grouping facts. The keys and grain must be defined carefully.
Check your understanding
Common mistake: Mixing different grains in one fact table can double-count measures, even when the diagram looks like a star.
What is the grain of a fact table?
Show explanation
What one row represents, such as an individual invoice line or a daily product total.
For your role
Choose your role to see what this term means in your work.
Why it matters
It makes reports faster, simpler to build and less prone to double counting than one wide table or many tangled ones.
Where it is used
Data warehouses and BI semantic models. Used by BI developers, data engineers, analytics engineers and data analysts.