DAX

Data Analysis Expressions (DAX) is the formula and query language for Power BI, Microsoft Fabric semantic models, Power Pivot in Excel, and Azure Analysis Services Tabular models. It looks superficially like Excel formulas but operates over columns and tables, not individual cells, with semantics around filter context and row context that take time to internalise. Used for calculated columns (per-row calculations in the model), measures (aggregations evaluated in the current filter context), row-level security predicates, and table-valued queries. Mastering DAX is the difference between a usable Power BI model and a powerful one — it unlocks time intelligence, complex aggregations, and dynamic analytics.