Database constraints can easily validate data entries and enforce referential integrity, both of which are commonly reported sources of data errors. CHECK constraints can prevent a keypunch operator from successfully typing values into a table column that are outside the range of values permitted for that column by enterprise business rules, and referential integrity constraints can prevent child table rows from becoming orphaned as the result of a mistaken deletion of a parent table row or update to a parent table primary, or alternate, key.
Constraints are a physical implementation of the business rules under which an enterprise operates. Integrity constraints restrict database updates to a set of specified values or ranges of values. Integrity constraints prevent bad data from entering the database and intertable relationships from corruption by the improper deletion or updating of the existing database.
- Semantic
- Physical
Vantage also provides a referential constraint, which provides the Optimizer with a means for devising better query plans, but which does not enforce the referential integrity of the database (see CREATE TABLE and CREATE TABLE AS ).