Understanding Data Modelling in Power BI: Joins, Relationships, and Schemas Explained

Introduction Working with raw data often introduces challenges such as duplication, inconsistency, and difficulty in extracting meaningful insights. Data modelling in Power BI addresses these challenges by structuring data into related tables, enabling efficient querying, accurate calculations, and scalable reporting. This article explores: SQL joins and their behaviour Power BI relationships and how they differ from joins Data modelling schemas Practical implementation in Power BI We’ll use a simple school dataset to ground these concepts. 1. Sample Dataset We will work with three core tables: Students (Dimension Table) StudentID Name Age Class 101 Alice 14 Form 2 102 Brian 15 Form 3 103 Catherine 14 Form 2 104 David 16 Form 4 Test Scores (Fact Table) ScoreID StudentID Subject Score 1 101 Math 85 2 101 English 78 3 102 Math 92 4 105 Science 88 ⚠️ Note: Student 105 does not exist in the Students table—this represents a referential integrity issue. 📊 View Dataset Online Explore the dat