Defining Views (!!)

Views are relations, except that they are not physically stored.

They are used to:

• simplify complex queries, and

• define distinct conceptual interfaces for different classes

of users.

Example view: purchases of telephony products.

CREATE VIEW telephony-purchases AS

SELECT product, buyer, seller, store

FROM Purchase, Product

WHERE Purchase.product = Product.pname

AND Product.category = ‘telephony’

The view is materialized when its results are stored in the DBMS.

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