Custom data source joined with Standard doesn't work

Hi,

I have created join data source with standard data source(CODAPAHB) and custom data source(created for embedded custom BO for appointment).

These two data sources are linked with Appointment ID using left outer join.When I test this join data source, it is returning data from only one data source.Can you please suggest what is the issue and how to find out the issue?

Thanks

Jayasri