Exercise 3.20 Consider the following schema:Suppliers(sid: integer, sname: string, address...

Exercise 3.20 Consider the following schema:

Suppliers(sid: integer, sname: string, address: string)Parts(pid: integer, pname: string, color: string)Catalog(sid: integer, pid: integer, cost: real)

The Catalog relation lists the prices charged for parts by Suppliers. Answer the following questions:

• Give an example of an updatable view involving one relation.
• Give an example of an updatable view involving two relations.
• Give an example of an insertable-into view that is updatable.
• Give an example of an insertable-into view that is not updatable.