Describe the difference between a base relation and a view and discuss the main benefits of using views in a relational database.

Question

What will be an ideal response?

Answer 1

A base relation is a named relation, corresponding to an entity in the conceptual schema, whose
tuples are physically stored in the database. A view can be constructed by performing operations
such as the relational algebra selection, projection, join or other calculations on the values of
existing base relations. A view is the dynamic result of one or more relational operations
operating on the base relations to produce another relation. A view is a virtual relation that does
not actually exist in the database but is produced upon request by a particular user, at the time of
request.
The main benefits of views includes:
? It provides a powerful and flexible security mechanism by hiding parts of the database from
certain users. The user is not aware of the existence of any attributes or tuples that are
missing from the view.
? It permits users to access data in a way that is customized to their needs, so that the same data
can be seen by different users in different ways, at the same time.
? It can simplify complex operations on the base relations. For example, if a view is defined as
a join of two relations, the user may now perform the more simple unary operations of
selection and projection on the view, which will be translated by the DBMS into equivalent
operations on the join.