Date Filter for Count of Two Tables

I need Dashboard users to be able to use relative date + date range on the aggregate (count) of two separate tables - lets say departures + arrivals - the column I would connect to these filters has the same name - created_at in both tables. Can anybody give me some guidance ?

  1. Would it be possible without native SQL queries ? I tried that but not clear how it would work - given you connect the filter to one column
  2. I didn’t see a way to use Union in a question (not query)- is that not possible ? (Except workaround full outer join with no match)
  3. I don’t see correct way to combine results of two questions
    Thanks !

Only possible if you do a UNION of these two tables via SQL questions and then a filter on this query