Yes, Union is supported.I am assuming both the tables are in Incorta and you are using incorta over incorta SQLi to run this query?Can you try this query using MV - Spark SQL? 

@mkrieger query function works at row level and aggregate functions will not work.You need to aggregate data in a table and then query that table in query function.Please review this video for a similar use case:https://www.youtube.com/watch?v=9CdKnT...