Hi Bront,

This is unfortunately true. In our documentation here, we even state that:

"Note that you cannot create joins across data sources, including joins between external and internal schema on LabKey Server."

https://www.labkey.org/wiki/home/Documentation/page.view?name=externalSchemas

The only way I've ever seen joins like that work on external datasources is when the external datasource is used as a synonym if you're using MS SQL rather than Postgres. So you could potentially mount tables and views from a different schema or DB, but have them work in LabKey as if they were local.

https://msdn.microsoft.com/en-us/library/ms187552.aspx

Regards,

Jon