For Zaufany learners
The Double-Count Trap
Joining Orders and Order Items made delivery fees triple overnight. Fix the table grain.
- 1-to-many table relationships (Orders to Order Items)
- Why summing header columns on a joined table multiplies them
- Star-schema basics: fact tables vs lookup tables
This level is part of Zaufany's Power BI & Data Analytics training. Levels 1 and 2 are free for everyone.