Object views, like traditional views, hide
the details of the underlying table joins and allow object-oriented development and processing to
occur in the database while the underlying tables are still in a relational format.
20 Oracle Database 11g DBA Handbook
In the following subsections, I??™ll review the basics of the types of views a typical database
user, developer, or DBA will create and use on a regular basis.
Regular Views
A regular view, or more commonly referred to as a view, is not allocated any storage; only its
definition, a query, is stored in the data dictionary. The tables in the query underlying the view
are called base tables; each base table in a view can be further defined as a view.
The advantages of a view are many. Views hide data complexity??”a senior analyst can define
a view containing the EMPLOYEE, DEPARTMENT, and SALARY tables to make it easier for upper
management to retrieve information about employee salaries by using a select statement against
what appears to be a table but is actually a view containing a query that joins the EMPLOYEE,
DEPARTMENT, and SALARY tables.
Views can also be used to enforce security. A view on the EMPLOYEE table called EMP_INFO
may contain all columns except for salary, and the view can be defined as read only to prevent
updates to the table:
create view EMP_INFO as
select Employee_Number, Last_Name,
First_Name, Middle_Initial, Surname
from EMPLOYEE
with READ ONLY;
Without the read only clause, it is possible to update or add rows to a view, even to a view
containing multiple tables.
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