Star Schema Design for Power BI
Optimal data modeling patterns for business intelligence.
Star schema is the gold standard for Power BI data modeling, providing optimal performance and usability.
What is Star Schema?
A dimensional modeling pattern with: - Central fact tables (transactions, events) - Surrounding dimension tables (descriptive attributes) - Clear, simple relationships
Why Star Schema?
Performance - Efficient query patterns - Minimal joins needed - Optimized storage
Usability - Intuitive for business users - Natural groupings - Easy to navigate
Flexibility - Supports various analyses - Easy to extend - Reusable patterns
Designing Fact Tables
Characteristics - Contain measurements (amounts, counts) - Foreign keys to dimensions - Grain defines detail level - Often largest tables
Best Practices - Clear, consistent grain - Numeric measures only - Integer keys for relationships - Remove text descriptions
Designing Dimension Tables
Characteristics - Descriptive attributes - Primary key (surrogate key) - Hierarchy levels - Business-friendly names
Best Practices - Include surrogate keys - Denormalize for performance - Handle slowly changing attributes - Add useful hierarchies
Relationship Guidelines
- Single direction (fact to dimension)
- One-to-many only
- Integer keys
- No bi-directional unless required
Common Patterns
Date Dimension Every model needs dates: - Full date range - Hierarchy (Year > Quarter > Month > Day) - Fiscal periods if needed
Conformed Dimensions Shared across facts: - Customer dimension - Product dimension - Geography dimension
Frequently Asked Questions
Why is star schema recommended for Power BI?
Star schema provides optimal performance because Power BI is designed for dimensional models. It reduces query complexity, improves compression, and creates intuitive models that business users can understand and navigate easily.
Should I always use surrogate keys?
Yes, integer surrogate keys are recommended for relationships instead of natural keys. They improve performance, handle changing source values, and ensure reliable relationships even if source keys change.