I would like to know if it is possible to use an MDX query as an data source.
It is not. Sorry - You'll need to point Tableau directly at the cube in question. At that point, you COULD create a calculated member which encapsulates some MDX, though.
How to Create a Calculated Member
Hope this helps!
Become a Viz Whiz on the Forums!
Support the Community and master Tableau.
Retrieving data ...