Sometimes we may need to join the tables from different schemas in RPD. Lets go through with simple example. Assume there are two schemas in the same Oracle Database called Schema-1 and Schema-2 and we have imported the tables Sales-Daily from Schema-1 and Dim_Date from Schema-2 into Physical layer as below.
Now, to join the table Sales-Daily from Schema-1 and Dim_Date from Schema-2, we need to select the tables and right click for options, select "Physical Diagram" => "Selected Object(s) Only" from the options.
Next, define the join condition.
Next, bring both the tables under on BMM Layer. 