Please identify your CR version. You can read about enforced joins in the Help section, which is about the only place you will find any info on this. Assuming you have a version that allows you to use "enforce joins", then the following is true. If you have two tables table1 and table2 with an equal join, and you add only a field from table1 and do not enforce the join, the join will be ignored and the second table will have no impact on the number of records returned. If you then add a field from the second table, the join will be "enforced" and only records with matching fields in both tables will be shown. By using "enforced join" this same behavior will occur WITHOUT adding a field from the second table.
-LB