DAX Guide
by Marco Russo, Alberto Ferrari · SQLBI
Auto-updated reference for all 600+ DAX functions, operators and statements, with parameter details, version compatibility across Power BI and Analysis Services, and notes on how each function behaves inside row and filter context. Goes beyond Microsoft's own function reference by annotating context transition and evaluation-context behaviour per function, which is exactly where practitioners get burned.
More resources on Power BI & Tableau
Dashboards That Deliver: How to Design, Develop, and Deploy Dashboards That Work
Tool-agnostic guide to the full dashboard lifecycle: requirements gathering, discovery, prototyping, release and maintenance, with annotated real-world dashboards from healthcare, finance, marketing and transport. Readers learn to manage stakeholders and deliver dashboards that people actually use.
Workout Wednesday
Weekly challenge archive where you rebuild a published visualization in Tableau, Power BI or Sigma from a screenshot plus written requirements, then compare against the author's solution. Includes a WOW Essentials track for newer users.
Tableau Level of Detail Expressions: Overview and Order of Filter Operations
Tableau's official reference on FIXED, INCLUDE and EXCLUDE expressions, plus the order in which extract, context, dimension and measure filters execute. Explains why a FIXED calculation ignores your dimension filter and how to make it respect one. LOD expressions are Tableau's equivalent of DAX filter context - the concept nearly everyone gets wrong. This page treats granularity and filter ordering as a model rather than a recipe, which is what separates competent Tableau authors from click-path users.
Understand Star Schema and the Importance for Power BI
Microsoft guidance on shaping Power BI semantic models as star schemas with fact and dimension tables. Covers surrogate keys, snowflaking, role-playing, slowly changing, junk and degenerate dimensions, and factless fact tables for many-to-many relationships, so models perform well and totals stay correct.
The Definitive Guide to DAX: Business Intelligence for Microsoft Power BI, SQL Server Analysis Services, and Excel, 2nd Edition
Russo and Ferrari's second edition covers table functions, evaluation contexts, CALCULATE and CALCULATETABLE, variables, calculation groups and the VertiPaq storage engine, ending with query plans and optimisation. The reference text for DAX beyond simple aggregations. The only text that explains filter context, context transition and the engine underneath rigorously enough that readers stop writing DAX by trial and error.
Introducing DAX Video Course
Free 150-minute course from Marco Russo and Alberto Ferrari covering calculated columns, measures, iterators, row and filter context, CALCULATE, relationships and time intelligence. Finish it and you can predict why a DAX measure returns the number it does. The single best free on-ramp to DAX that teaches evaluation context as a mental model rather than a formula cookbook.