Difference between union and append


#1

Is there an efficiency difference between the union function in dax and append in the query mode? And should I favor one over the other?

At the end of the day, I’m looking for the best option to load/run my model faster.


#2

I think if you can use append I would prefer that. Reason is because it’s likely much quicker to use the query editor for these transformations rather than DAX (calculated tables).

UNION does have some great uses when working with calculated tables and being able to combine many of these, but this would be my second option always if the I could do it in the query editor first.