LANSA table definitions can contain three types of columns:
Real fields
These are the normal fields found in any table definition and are assembled together to form the record format of the associated physical table. Such fields actually exist in the database table and their content (or value) can be extracted from any record in the table at any time. (Refer to Adding Real Fields to a Table.)
Virtual columns
These are columns that do not actually exist in the IBM i database table, but are dynamically derived from "real" fields in the table. (Refer to 1.6.4 Virtual Column Development.)
Predetermined join columns
These are columns defined on access routes to receive information retrieved from the table accessed by the access routes. (Refer to 1.6.6 Access Route Development and 1.6.7 Predetermined Join Column Development.)
