Query for feature to have business logic apply on multiple data sources

I know there is an option of using “mixed” to gather data from multiple data sources (eg. two mysql database) show it as table in the panel. I want a feature where we can apply business logic like joining the two tables and only giving values based on the join condition. Right now I can’t find a way to join two tables from two DBs.

This is needed because it has the capability to join tables from same data source in a sql query, but not from two databases using a SQL query.