Rules that you set to establish and preserve relationships between tables when you add, change, or delete records. Enforcing referential integrity prohibits users from adding records to a joined table for which there is no primary key, changing values in a primary table that would result in orphaned records in a joined table, and deleting records from a primary table when there are matching related records.
If you select the dbRelationDeleteCascade or dbRelationUpdateCascade option for a relationship, the Microsoft� Jet database engine allows changes and deletions, but changes or deletes related records to make sure the rules are still enforced.
Microsoft Jet version 4.X, through the Microsoft OLE DB Provider for Jet, exposes a much richer set of ANSI SQL and also exposes the ANSI cascade NULL referential action.