Referential Integrity in Access ’97
A value cannot be entered in the foreign key field of the related table if that value doesn't exist in the primary key of the parent table. A Null value in the foreign key is allowed, specifying that the records are unrelated.
- A record cannot be deleted from a parent table if matching records exist in a related table.
- A primary key value in the parent table cannot be changed, if that record has related records.
Determined by MS Access on the basis of primary key settings.