e) Referential Integrity

Define referential integrity

The process of ensuring consistency

What does referential integrity ensure?

That information is not removed if it is required elsewhere in a linked database.

Why can’t a database in a relational database relationship be deleted?

As it is linked to another database, therefore to keep referential integrity rules it can’t be deleted.

What is a foreign key constraint?

A foreign key in one table must match a primary key in another table, or it must be null.

Give an example of a foreign key constraint using the table Orders, foreign key CustomerID and the Customers table:

If a table Orders has the foreign key CustomerID pointing to the Customers table, the CustomerID in Orders must correspond to an existing CustomerID in Customers.