Appendix A. Commonly Used DAX Expressions
In this appendix, I will go over the syntax of some of the most commonly used DAX functions in Power BI. These are organized by section, then alphabetically within that section. For each function, there will be a brief description of the purpose of the function, the syntax of the function, and then an example using that syntax.
This is not an exhaustive list of all the functions in the DAX language. That can be reviewed at âDAX Function Referenceâ.
As with many things, DAX is a prime example of the Pareto principle: 80% of all the problems (outputs) can be solved with 20% mastery (inputs).
Aggregation Functions
AVERAGE
Definition
Returns the average (mean) of all the numerical values of a column.
Syntax
AVERAGE ( [ColumnName] )
Example
AverageScore = AVERAGE ( GradeScore[Score] )
AVERAGEX
Definition
Calculates the average (mean) of a set of expressions evaluated over each row of a table.
Syntax
AVERAGEX ( 'TableName' , <expression> )
Example
AverageScorePercentage = AVERAGEX ( 'GradeScores', 'GradeScores'[Score] + 'GradeScores'[MaximumPossibleScore] )
COUNT
Definition
Returns the number of records for a column that are not blank.
Syntax
COUNT ( [ColumnName] )
Example
CountOfStudents = COUNT ( 'UniversitySuppliedData'[StudentID] )
DISTINCTCOUNT
Definition
Returns the number of distinct values for a given column.
Syntax
DISTINCTCOUNT ( [ColumnName] )
Example
CountOfStudents = DISTINCTCOUNT ( 'GradeScores'[StudentID] ...
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