DAX MASTERY: CALCULATE, FILTER CONTEXT, TIME INTELLIGENCE, CALCULATION GROUPS, RLS

DAX Mastery is the fourth volume of the Advanced Excel & Data Modeling series — a complete, production-oriented guide to the language behind Power BI, Power Pivot, and Fabric. It opens with the two evaluation contexts — row and filter — that explain every DAX result. Then it moves through CALCULATE and its filter modifiers, time intelligence (SAMEPERIODLASTYEAR, DATEADD, YTD/QTD/MTD, rolling windows, semi-additive measures), advanced patterns (variables, iterators, context transition, relationships, TREATAS), and calculation groups that turn 80 measures into 18 objects. The final parts cover row-level security with USERPRINCIPALNAME, object-level security, DAX Studio, the VertiPaq engine, and model-level optimization — followed by three full case studies: financial reporting, retail analytics, and SaaS metrics. Every chapter is code-first, with comparison tables, performance numbers, and worked examples you can paste into DAX Studio and run. By the end you will think in contexts, not formulas.