Referential Integrity is a relation database concept which means that the table relationships must always be consistent. Any foreign key field must agree with the primary key that is refeerenced by the foreign key.Any primary key field changes must be applied to all the foreign keys or not applied at all. The same restrictions also applies to foreign keys in that any updates must be propogated to the primary key. Example- To uniquely identify each customer in a CUSTOMER table a primary key coloumn with name CUSTOMER_ID is created. to identify a customer and bank account relationship in the ACCOUNTS table an existing customer must be referenced. That is why the CUSTOMER_ID coloumn created in the ACCOUNTS table is a foreign key. This coloumn is special as its values are not newly created. these values must reference existing and identical values in the primary key coloumn of another table that is the CUSTOMER_ID coloumn of the CUSTOMER table. Referential integrity is a standard that means any CUSTOMER_ID value in the CUSTOMER table may not be eddited without edditing the corrosponding value in the ACCOUNTS table.