Custom SQL Plus another Datasource

I have a dashboard that is using custom sql to pivot ticket data. Something like the below. It has worked to allow me to create dashboards based on that table. Now I need to do some filtering by columns in another table. Can you *** the 2nd table in the same dashboard and join it to the custom query assuming it has a common field. So the datasource tab would have Custom SQL QUery plus another table that are joined?

SELECT [CASENBR]

      CASE_NBR

       ,CREATED_DT

      ,CREATED_DT as [Date Used]

      ,CLOSED_DT

      ,'Opened' as [Event]

      , +1 As [Total]

  FROM table1

UNION ALL

SELECT [CASENBR]

       CASE_NBR

      ,CREATED_DT

      ,CLOSED_DT

      ,CLOSED_DT as [Date Used]

      ,'Closed' as [Event]

, -1 As [Total]

  FROM table1