Multi column joins and Federated Tables

I am having a problem with getting information from two tables in our databases.

Table A is a federated table from our accounts server which works perfectly开发者_C百科 well if queried on its own. It has no unique ID field, but Job and Code fields are unique

Table B is an analogue to Table A on our Production server and has Job and Code fields that should match those in the Accounts server.

I would like to create a query that gives me all the Codes in table A that do no exist in table B for a given Job.

When I try and perform any query that links Table A and Table B directly I get Connection Errors - is this something that is outside the scope of Federated Tables?