Non-Updatable Views

CREATE VIEW Seattle-view AS

SELECT seller, product, store

FROM Person, Purchase

WHERE Person.city = ‘Seattle’ AND

Person.name = Purchase.buyer

How can we add the following tuple to the view?

(‘Joe’, ‘Shoe Model 12345’, ‘Nine West’)

In principle, two tuples should be added to the database:

Person: (foo, NullPhoneNumber, ‘Seattle’)

Purchase: (foo, ‘Joe’, ‘Nine West’, ‘Shoe Model 12345’)

But it’s very hard to manage the foo’s later, so this update is not legal.