In our My Sum Debug measure, we simply substitute the CONCATENATEX function for the SUMX function present in the My Sum measure. Thus, when debugging our measure, we can essentially take a peek inside the table that SUMX is iterating over in order to see the individual values that make up our calculation since our My Sum Debug measure now returns the individual values that comprise the calculation.
This technique can be used with any of the iterator functions, such as SUMX, AVERAGEX, COUNTX, and MEDIANX. In addition, this technique can also be used with any table created within a DAX expression. Seeing the individual values that comprise otherwise hidden, internal DAX tables can greatly aid in the troubleshooting and debugging of measure and column calculations.