How to do source checks for a target table having couple source staging table. Transformations are simple unions.

I am trying to do source to table consistency checks using Collibra. Source checks helps me doing that but in case if there are more than 1 source table for a target table, how do I setup the source checks using Collibra DQ UI? The ETL code shows me that they have created the target table with some basic union queries from the two staging tables. Someone suggested if there is a way to form a temporary table which is an union of staging tables and then run source checks by pointing the merged table as source to the target table? Thoughts?