13. DAX: Data Analysis Expressions
13.1 What is DAX?
In short: DAX (Data Analysis Expressions) is the formula language of Power BI, Analysis Services and Power Pivot in Excel.
DAX (Data Analysis Expressions) is the formula language of Power BI, Analysis Services and Power Pivot in Excel. It looks similar to Excel formulas, but there is one big difference: Excel formulas work on cells, DAX works on tables and columns. You never refer to "cell B2"; you refer to Orders[Amount] and let the context decide which rows are included.
You write DAX in three places:
| Object | Created with | Evaluated | Stored |
|---|---|---|---|
| Calculated column | Table tools › New column | Row by row, at data refresh | Stored in the model (uses memory) |
| Measure | Home › New measure | At query time, in the current filter context | Not stored – only the formula |
| Calculated table | Modeling › New table | At data refresh | Stored in the model |
Ravindra Bagale's Tip
Mitrano, khup students start DAX by writing long formulas copied from the internet. Start with simple base measures (Total Sales, Total Orders) and build new measures on top of them. Understanding filter context matters much more than memorising function names. Ha niyam lakshat theva.