5.3.2. Data Modeling Concepts (Dimensions, Facts, Hierarchy)

💡 First Principle: A Power BI data model consists of tables, relationships, and calculations (DAX) designed to enable dynamic analysis. The model determines what questions users can ask—a poorly designed model limits insights no matter how good the visualizations are.

• Dimensions: Descriptive attributes (who, what, where, when) used to filter and group data—the "by" in "sales by region."
• Facts: Numeric, measurable data (sales amount, quantity) stored in central fact tables—the numbers you're analyzing.
• Hierarchy: A structure within a dimension that allows users to drill up and drill down (e.g., Year → Quarter → Month → Day).
• Relationship: Links between tables (typically 1:many) based on matching columns (keys).