OVERVIEW OF MAJOR COMPONENTS - Database Design and Development: An Essential Guide for IT Professionals - page 47

database or only to some parts. Access privileges also cover privileges to retrieve,
add, update, or delete data. When circumstances change, database administrators
may also need to revise the initial authorizations and revoke the privileges. DCL
provides commands extending to various types of granting and revoking data access
privileges.
Query Interface A database query is a request for information. A query may take
the form: “Display all the customers in the country of Switzerland who bought
products from Japanese manufacturers during the prior month.” Or the query may
just relate to one customer: “Display the last three orders from customer 1234.”
When a programmer or a user submits a query, the query interface interprets,
optimizes, executes the query, and displays the result.
Report Writer This is another interface between the programmer or user and the
database. Many types of report writers exist. At a minimum, a report writer allows
a programmer to construct a report with proper headings, page breaks, and totals.
It also includes a method for submitting the reports for execution and printing them.
Application Developer The application developer comprises software for creat-
ing applications. Mostly used by programmers, the application developer enables
them to combine input forms, reports, menus, submenus, and application logic to
create program modules and then to pull all of these together as specific applica-
tions that can be used by various groups of users.
FUNCTIONS AND FEATURES
We have looked at the individual components that make up the database environ-
ment in an organization. Briefly, we have seen the hardware, software, and people
components. You have observed how the various pieces fit together and support the
environment. You have gained a broad understanding of database management
systems and the necessity for such sets of specialized software.
Each component in the environment serves a special purpose. Each component
is required to perform certain functions. To serve its designated purpose, each com-
ponent is equipped with specific features. For example, the modern storage devices
have fault-tolerant features that help the continued functioning of the database
despite hardware malfunctions. If you want to appreciate why the various compo-
nents exist in the database environment, you have to study the functions and
features. Let us go over the major components and examine their functions and
features.
Hardware
Hardware, of course, forms the underlying basis of the infrastructure. The collection
of physical devices for storing and processing of data in the database constitute the
hardware in the environment. Remarkable progress in hardware components
during the last few decades has promoted the use of database systems. Apart from
the physical storage devices, other pieces of hardware support the processing and