Because database objects may be related in more than one way, you must define the joined column using the specific relationship involved, i.e. the role defined for the parent-child relationship between the two database objects.
You can also have an object borrow values from a parent, which itself has borrowed the values from a grandparent. In this way it is possible to create joined columns over parents, grandparents, great-grandparents, etc. Performance may be adversely affected, however, because of the time needed to query the database.
NOTE 1: Joined columns MUST be based on the same domain as the parent column they take their values from.
NOTE 2: Joined columns, whether specified in the Definer or inserted via the Windows Designer, cannot be accessed by means of ODBC.
NOTE 3: Joined columns cannot retrieve values from the supertype of the parent in a relationship. The workaround is to define Extra Query columns, as described in the USoft Windows Designer Help.