Databases Reference
In-Depth Information
INTRODUCTION
The better your database design, the better it will meet your business and appli-
cation requirements. This means collecting business data, identifying entities and
relationships, and then converting them to database tables. All this is done with
your final goal in mind, implementing your physical database.
Before you can begin creating database tables you need to finish the remaining
details of your database design. Review the physical design requirements and
how they impact your final design. These include not only data requirements,
but application requirements and requirements relating to the environment in
which the database will be deployed. It may be necessary to make additional
adjustments to your design to more accurately reflect the real world. Now you
must not only consider entities and attributes, but also the volume of data that
you must support and how it impacts your physical design requirements.
With the design process out of the way, you're ready to implement the design
and deploy your database. Even here, there are additional decisions to be made.
These relate to how to create database objects that match your design. The
process starts with database tables and continues on through other database
objects as needed, such as indexes and views.
5.1 Physical Design and Implementation
The process of completing E-R diagrams, data normalization, and conversion to
relational tables does not represent the end of the design process. At best, these
steps can be considered the end of the beginning. There is still work to be done
before you can implement the tables you've designed and prepare to deploy your
database solution. The process brings you to the starting point for physical data-
base design.
In order to determine how best to modify the tables to improve application
performance, a wide range of factors must be considered. The factors will help
determine which modification techniques to apply and how to apply them.
5.1.1 Understanding Design Requirements
Keep in mind that design is an ongoing process and the dividing lines between
design phases can become vague over time. Even as you move into the final design
phases you may find it necessary to perform more data gathering as new questions
arise. The new information is applied to your design to try to create the model that
matches your needs as closely as possible in a relational database model. The
remaining process is often considered to be as much art as science. The choices are
so numerous and the possible combinations of modifications are so complex that
even an experienced designer hopes for a satisfactory, but not a perfect, solution.
