Defining Views (!!)
Views are relations, except that they are not physically stored.
- simplify complex queries, and
- define distinct conceptual interfaces for different classes
Example view: purchases of telephony products.
CREATE VIEW telephony-purchases AS
SELECT product, buyer, seller, store
WHERE Purchase.product = Product.pname
AND Product.category = ‘telephony’
The view is materialized when its results are stored in the DBMS.