Improved data integrity Database integrity refers to the validity and consistency of stored data. Integrity is usually expressed in terms of constraints, which are consistency rules that the database is not per- mitted to violate. Constraints may apply to data items within a single record or they may apply to relationships between records. For example, an integrity constraint could state that a member of staff’s salary cannot be greater than £40,000 or that the branch number contained in a staff record, representing the branch where the member of staff works, must correspond to an existing branch office. Again, integration allows the DBA to define, and the DBMS to enforce, integrity constraints.