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

This is a complete beginner guide covering: A) SQL Joins & Power BI Relationships SQL Joins Power BI Relationships B) Fact vs Dimension Tables, Star Schema, Snowflake Schema, and Common Concepts Fact Tables Dimension Tables Star Schema Snowflake Schema C) Modeling Issues Common Modeling Issues Diagrams SQL Code Step-by-step Instructions Data Modeling Explained Lets say, a retail company has three tables: Sales, Customers, and Products. We require to model the data by organizing data tables and defining how they connect to each other so that every sale is linked to the right customer and the right product thus be able answer business questions accurately. 1. SQL Joins A join combines rows from two tables based on a shared column. Before creating relationships in Power BI, understanding joins helps you know what data you are working with. We use two simple tables throughout all join examples below. Example Table A — customers id name country 1 Maria Germany 2 John USA 3 Georg USA 4 M