Variable Help

once defined, the variable is stored as constant value.  so in expression like:

Sales[Order Number]<=CurrentOrderNumber

the left part is a real variable row by row, the right part is actually a constant defined before. 

Hi RZAU ,

For understand VAR statement, you should understand the context concept in Power BI, because it is influence by context.

VAR: Stores the result of an expression as a named variable, which can then be passed as an argument to other measure expressions. Once resultant values have been calculated for a variable expression, those values do not change, even if the variable is referenced in another expression.

Please refer below notes for your dax formula:

Sales[Order Position] =
VAR CurrentOrderNumber = Sales[Order Number] //get current value for [Order Number] column according to the line context
VAR Postion =
    CALCULATE (
        DISTINCTCOUNT ( Sales[Order Number] ),
        Sales[Order Number] <= CurrentOrderNumber //use the CurrentOrderNumber to filter the [Order Number]column, now CurrentOrderNumber is just a value not a column
    )
RETURN
    Position

 For more details, you can read related document: VAR keyword (DAX) - DAX | Microsoft Learn , Variables in DAX - SQLBI

Best regards,
Community Support Team_Binbin Yu
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