Do the two fields in the ON portion of a join have to be the exact same datatype and length
Bala Krishna replied
There are certain restrictions in the database system, which mean that totally arbitrary combinations of fields cannot be linked together. Two fields can be linked only if both fields have the same data type in the Dictionary (including the length attribute). This means that two fields can be linked if they have the same domain. There are separate search functions for each table to assist in the search for suitable fields. Text, domains and data types can be searched for. The text search operates across the technical names of the fields as well as over the long texts. The Field documentation function can be used to find information about the technical definition of a field, so as to allow a specific search for suitable fields.
see the documentation