The name of a field (in the parent business component of the join object definition) that the destination table is joined on. The Source Field property must point to a field that represents a database column.
A computed field is an example of a field not based on a database column, and is therefore not suitable as a source field for a join specification.
The field has to be a foreign key with respect to Destination Column.
(+)This is required if the join occurs on a field other than ID.