•Suppose I
have only the result of SeattleView:
• SELECT buyer, seller,
product, store
• FROM Person, Purchase
• WHERE Person.city = ‘Seattle’ AND
• Person.per-name =
Purchase.buyer
•and I want to answer the query
• SELECT buyer,
seller
• FROM Person, Purchase
• WHERE Person.city = ‘Seattle’ AND
• Person.per-name =
Purchase.buyer AND
•
Purchase.product=‘gizmo’.
•Then, I can rewrite the
query using the view.