Database Reference
In-Depth Information
improperly, it will be difficult for you to retrieve certain types of information, and you'll
runtheriskthatyoursearcheswillproduceinaccurateinformation.
Inaccurate information
is probably the most detrimental result of improper database design—it can adversely af-
fect your organization's bottom line.
In fact, if your database affects the manner in which
your business performs its daily operations or if it's going to influence the future direction
of your business, you
must
be concerned with database design.
Let's look at this from a different perspective for a moment: Think about how you would
go about having a custom home built. What's the first thing you're going to do? Certainly
you're not going to hire a contractor immediately and let him build your home however he
wishes.
Surely
you will first engage an architect to design your new home
and then
hire a
contractor to build it. The architect will explore your needs and express them as a set of
blueprints, recording decisions about size and shape and requirements for various systems
(structural, mechanical, electrical). Next, the contractor will procure the labor and mater-
ials, including the listed systems, and then assemble them according to the drawings and
specifications.
Now let's return to our database perspective and think of the logical database design as the
architectural blueprints and the physical database implementation as the completed home.
The logical database design describes the size, shape, and necessary systems for your data-
base and it addresses the informational and operational needs of your business. You then
build the physical implementation of the logical database design using your RDBMS pro-
gram. Once you've created your tables, set up table relationships, and established the ap-
propriate levels of data integrity, your database is complete. Now you're ready to design
and create applications that allow you and your users to interact easily with the data stored
in the database, and you can be confident that these applications will provide you with
timely and, above all, accurate information.
Although you can implement a poor design in an RDBMS, implementing a good design
is far more to your advantage because it will yield accurate information, store data more
efficiently and effectively, and be easier for you to manage and maintain.
The Importance of Theory
Note
In this chapter, I use the term
theory
to represent “general propositions used as
principles” and not “conjectures or proposals.”
Anumberofmajordisciplines(andtheirassociateddesignmethodologies)havesometype
of theoretical basis. Structural engineers design an unlimited variety of structures using the
