The Definitive Guide to DAX is the most comprehensive and authoritative guide to Microsoft's DAX language for business intelligence and analytics. While other books cover only the basics, this guide offers expert guidance on everything intermediate-to-advanced Excel users and BI professionals need to know, from the basics to innovative high-performance techniques. Two leading Microsoft BI consultants and mentors introduce DAX through realistic and useful examples, presenting common calculations that empower users to get results immediately. Alberto Ferrari and Marco Russo demystify complex topics, showing readers exactly what happens under the DAX engine's "hood" when they run a DAX expression. Ferrari and Russo carefully walk through common scenarios where DAX may not be easy to grasp; show how to optimize data models so DAX expressions will run quickly; demonstrate how to write fast, robust DAX code; and guide you in clearing bottlenecks from existing code. Throughout, they demonstrate DAX at work in both SQL Server and Microsoft Excel environments, empowering you no matter which Microsoft BI or analytics platform you prefer.