Database Reference
In-Depth Information
theoriesofphysics.Composerscreatebeautifulsymphoniesandorchestralpiecesusingthe
concepts found in music theory. The automobile industry uses aerodynamics theories to
designmorefuel-efficientvehicles.Theaerospaceindustryusesthesametheoriestodesign
airplane wings that reduce wind drag.
These examples demonstrate that theory is relevant and very important. The chief advant-
ageoftheoryisthatithelpsyoupredictoutcomes;itallowsyoutopredictwhatwillhappen
if you perform a certain action or series of actions. You know if you drop a stone, it will
falltotheground.Ifyouareagile,youcangetyourtoesoutofthewayofNewton'stheory
of gravity. The point is that it works
every time.
If you chisel a stone flat and place it on
another flat stone, you can predict that it will stay where you put it. This theory allows you
to design pyramids and cathedrals and brick outhouses. Now consider a database example.
Let'sassumeyouhaveapairoftablesthatarerelatedtoeachother.Youknowthatyoucan
draw data from both tables simultaneously simply because of the way relational database
theory works. The data you draw from both tables is based on matching values of a shared
field between the tables themselves. Again, your actions have a predictable result.
The relational database is based on two branches of mathematics known as
set theory
and
first-order predicate logic.
This very fact is what allows the relational database to guaran-
tee accurate information. These branches of mathematics also provide the basis for formu-
lating good design methodologies and the building blocks necessary to create good rela-
tional database structures.
You might harbor an understandable reluctance to study complicated mathematical con-
cepts simply to carry out what seems to be a rather limited task. You're still sure to hear
claims that the mathematical theories on which the relational database and its associated
design methodologies are based don't have any relevance to the real world, or that they are
somehow impractical. This is not true: Math is central to the relational model and is what
guarantees the model's viability. But cheer up—it isn't really necessary for you to know
anythingaboutsettheoryorfirst-orderpredicate logicinordertousearelational database!
You certainly don't have to know all the details of aerodynamics just to drive an automo-
bile. Aerodynamics theories may help you understand and appreciate how an automobile
can get better gas mileage, but they won't help you learn how to parallel park.
Mathematical theory provides the foundation for the relational database model, and thus
makes the model predictable, reliable, and sound. Theory describes the basic building
blocks used to create a relational database and provides guidelines for how it should be ar-
ranged. Arranging building blocks to achieve a desired result is defined as “design.”
