Rules that ensures that data is accurate.
- Entity Integrity: no nll in pkey ( Null: no value in a key even not space. )
- Referential Integrity J (of reference) if a foreign key exists in a relation,
- either the foreign key value must match a candidate key value of some tuple in it’s
- home relation or the foreign key value must be wholly null.
- Enterprise Constraints: enterprise =organisation ..additional rules specified by the
- users or db admin of a db.