There are Three Integrity Rules. They are as follows:
Entity Integrity Rule: The Entity Integrity Rule enforces that the Primary key cannot be Null
Foreign Key Integrity Rule: The FKIR denotes that the relationship between the foreign
key and the primary key has to be enforced. When there is data in Child Tables the
Master tables cannot be deleted.
Business Integrity Rules: The Third Integrity rule is about the complex business processes
which cannot be implemented by the above 2 rules.
