SQL Developer Data Modeler

Hi all,

I am trying to compare/merge or just trying to merge a relation model with another in Oracle SQL Developer DATA MODELER.

Scenario:
I have tried to import from data dictionary the hr schema into 3 parts.
Table employee is alone imported in one design model's relational model(say DataModelerDesign1- DMD1).
Table Departments,Locations and Countries in another design model's relational model(say DMD2).
Table Job_history,Jobs and Regions in another design model's relational model(say DMD3).
Now, I tried to merge all this into one design model's relational model, here into DMD3.

Requirement:
I want all of this relational model's tables to get merged with exact mappings as if it is in HR schema all connected to each other. But they are all getting merged as separate entities not conencted to each other when taken from Compare/merge option. How should i do this task?

Issues:
1) I can never see anything in the compare model when i try to click on view compare mapping. Can anytime we see any data here?
2) In realtime scenario, when will we try to merge a table into another or split it. Because some foriegn key violations are happening here. Is it ever possible to succeed our requirement while merging itself instead of creating relationships between entities manually in main relationship model DMD3 in example here.