Within a database, referential integrity (RI) is a system of data rules or constraints that the database automatically enforces. One such rule detects "cascading deletes"; this means that the database cannot delete a record that references another record. In this case, the two records have a foreign key relationship that must be maintained.
As another example, a "uniqueness" constraint means that the database cannot insert a record that would duplicate an existing record. In the case of the Corporate Media Library, the value of a library item's bar code field cannot be identical to that in another record.