SQL Views and System Security - Database Systems - page 265

Example 13: Referring to the college database of earlier discussions, develop a set
of logical views that allow department heads to have access to student information if and
only if the student is enrolled in a major offered by that department:
Note: You can block direct access to data in a base table (for example Student ), and
force users to access the data through logical views on the table. These logical views can
in turn have restricted access to specific users as illustrated.
Security via Database Design
In addition to views, a database designer may design database tables with security
attributes that will subsequently be used to control user access. Only authorized users
will have access to these security attributes, but they can be used to block other users
from accessing sensitive data. However, you would be required to create and maintain
some additional tables (an example of this approach appears in [Foster, 1999]).
13.3 Materialized Views
Oracle supports database objects called materialized view s. A materialized view is a
database object that stores the results of a query. It differs from the traditional logical view
in that whereas the logical view stores the definition of the query, the materialized view
stores the result of the query. A materialized view would therefore qualify as a snapshot
relation (review chapter 3). A full discussion of materialized views is beyond the scope of
this course; however, a brief introduction is worthwhile.
The From-Clause of the sub-query that feeds a materialized view can name
tables, views, and other materialized views. Collectively these are called master tables
(a replication term) or detail tables (a data warehouse term). Databases that contain the
master tables are called the master databases .