Star Schema vs Flat Table: Which Should You Use in Power BI?
Data Model Design Matters
Your data model is the foundation. Get it right, and everything else is fast. Get it wrong, and no DAX optimization will save you.
Star Schema: When to Use It
A star schema has a central fact table surrounded by dimension tables. Use it when:
**Pros:** Efficient calculations, RLS-friendly, normalized, scalable
**Cons:** More complex model, needs more setup
Flat Table: When to Use It
One big table with all dimensions denormalized. Use it when:
**Pros:** Simple, easy to understand, fast to build
**Cons:** Slower at scale, harder to maintain, harder for RLS
The Hybrid Approach
Most of our clients use a hybrid: one main fact table with 5-10 key dimensions, plus an aggregated summary table for high-level dashboards. This gives you the best of both worlds.
Performance Impact
We tested a 5M-row sales dataset:
The star schema won because filters cascade down efficiently through relationships.
**Recommendation:** If you're debating this, go star schema. It scales better as your business grows.
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