Power BI Many-to-Many Relationships Explained: Why You Should Never Merge Fact Tables

Learn why you should never flatten two fact tables in Power BI and how to compare measures like sales and inventory without creating duplicate rows or incorrect calculations. In this lesson, you'll discover the importance of common granularity, how many-to-many relationships affect reporting, why shared dimensions are safer, and how poor modeling choices can lead to misleading results. This video is part of the Power BI Advanced Course, designed for beginners who want to build a strong foundation in business intelligence and data analytics using Power BI. 📚 Watch the Full Course Playlist:    • Power BI Advanced   Download the exercise files used in the lesson: https://powerbitraining.com.au/power-... 💼 Work With Me: We help businesses and professionals build high-quality Power BI solutions and become data-driven: → Corporate Training (2–5 days, in-person or online) Master Power BI, DAX, data modeling, and report design https://powerbitraining.com.au/ → Consulting Data model audits, performance optimization, and BI strategy https://amzconsulting.com.au/ → Coaching 1-on-1 programs to become a job-ready Power BI analyst https://coaching.amzconsulting.com.au/ ⸻ 🌏 Based in Sydney | Working with clients globally 📧 info@amzconsulting.com.au 🌐 https://amzconsulting.com.au/ 💼 LinkedIn:   / trainernoorani   ⸻ 0:00 Introduction 0:29 Understanding Many-to-Many Relationships 0:43 Finding the Lowest Common Granularity 1:19 What Happens When You Go Below the Common Grain 3:05 Designing the Model for Report Authors 4:45 Adding Descriptions & Guidance to Your Data Model 5:40 Comparing Sales vs Inventory Visually 6:20 Comparing Three Months of Sales with Stock on Hand 7:29 Date Slicer vs Date Hierarchy 8:18 Why Fact Tables Shouldn’t Be Connected Directly 9:53 Why You Can’t Flatten Two Transaction Tables 10:51 What Happens When You Merge Fact Tables 11:38 Why VLOOKUP Creates Duplicate Values 12:18 How Flattening Fact Tables Creates Incorrect Results #PowerBI #DataAnalytics #businessintelligence