Diagnosis
You attempted to link an additional table or define an additional fieldin an InfoSet which uses a table join.
Although a table join contains several tables, a sequence of recordswith the same structure is processed, i.e. there are no hierarchicalrelationships between the individual tables. Therefore, an InfoSetwhich uses a table join should be regarded as the same as an InfoSetwhich directly reads a table.
All tables in the join are filled with values at the same time (when arecord is processed). Consequently, it is irrelevant to which table inthe join you assign the additional table or the additional field. Fortechnical reasons, the first table is always chosen.
Note that, in the case of a table join when formulating the WHEREcondition or sections of code, you can always access all fields of alltables involved in the join.