DAX (Data Analysis Expressions):
DAX is a programming language used in Power BI to enhance existing data models.
It includes a library of functions, operators, and constants.
These components are used in formulas or expressions to fill in missing information in the data model.
Functions play a crucial role in DAX formulas, allowing you to perform tasks like aggregation and calculations.
Commonly used DAX formulas and functions include CALCULATE, SUM, and AVERAGE.
Formula Syntax:
A DAX formula starts with the name of a new calculated column or table, followed by an operator (usually an equal sign).
Next, you specify the DAX function and enclose its logic within parentheses.
Context in DAX:
DAX computes formulas within a context.
The evaluation context is the surrounding area of the cell where DAX evaluates and computes the formula.
Row context refers to the current row being evaluated within a calculation.
Filter context considers the filter constraints applied to the data, determining which rows or subsets are included or excluded from the calculation.
Calculated Tables and Columns:
Calculated tables: These are new tables created within a data model, based on data from different sources.
Calculated columns: These are new columns added to existing tables, presenting the results of specific calculations.