Consider the Oracle Virtual Private Database $($VPD$)$ feature described in Sec$-$

tion $9\mathrm{.}8\mathrm{.}5$ and an application based on our university schema.

a$.$

What predicate $($using a subquery$)$ should be generated to allow each fac$-$

ulty member to see only takes tuples corresponding to course sections

that they have taught?

b$.$ Give an SQL query such that the query with the predicate added gives

a result that is a subset of the original query result without the added

predicate.

c$.$ Give an SQL query such that the query with the predicate added gives

a result containing a tuple that is not in the result of the original query

without the added predicate.