Database Reference
In-Depth Information
SQL Views and System
Security
Two very powerful and important features of SQL are the facility to create and manage
logical views, and the capability to manage security issues of a database. This chapter
discusses these two related issues. The chapter proceeds under the following subtopics:
•
Traditional Logical Views
•
System Security
•
Materialized Views
•
Summary and Concluding Remarks
13.1 Traditional Logical Views
As pointed out in Chapter 3, a logical view is a virtual relation that allows end users to
access information in a manner that is consistent with their requirements. Any creditable
DBMS will allow the creation and manipulation of logical views. Following are a few
important points about views:
•
SQL views allow for logical interpretation of information in the
database.
•
Views include virtual, named (but not base), and derived
relations; these significantly help to comprise the external schema
of the database (review chapter 2).
•
Like named relations, views are created, and dropped using
the
Create
and
Drop
statements. However, views cannot be
structurally altered; they are virtual relations that are created and
dropped as the situation dictates.
•
Views are stored in the system catalog.