I have 2 MapInfo tables that have a corresponding unique ID number field. I'd like to be able to manually select some objects from one table and join the 2 tables based on a matching unique ID number for the selected objects only.
Is this possible?
Yes, this is possible.
You do it like regular SQL, but use the MapInfo user interface.
Here's an example: http://web.pb.com/mapinfopro-sep-2012/Query-Ninja-Joining-Tables
And here's an image showing how (from the above URL).
In order to achieve the result you're after, try these steps: