Java Reference
In-Depth Information
Chapter 1: Relational Databases
In This Chapter
The purpose of this chapter is to lay the groundwork for the rest of the topic by explaining
the underlying concepts of Relational Database Management Systems. Understanding
these concepts is the key to successful Java database programming. In my experience,
just understanding how to handle the Java side of the problem is not enough. It is
important to understand how relational databases work and to have a reasonable
command of Structured Query Language (SQL) before you can do any serious Java
database programming.
Understanding Relational Database Management Systems
A
database
is a structured collection of meaningful information stored over a period of
time in machine-readable form for subsequent retrieval. This definition is fairly
intuitive and says nothing about structure or methodology. By this definition, any file
or collection of files can be considered a database. However, to be useful in practical
terms, a database must form part of a system that provides for the management of
the data it contains. Seen from this perspective, a database must be more than a
mere collection of files. It must be a complete system.
A
practical
database management system combines the physical storage of data with
the capability to manage and interact with the data. Such a system must support the
following tasks:
Creation and management of a logical data structure
Data entry and retrieval
Manipulation of the data in a logical and consistent manner
Storage of data reliably over a significant period of time
Prior to the development of modern relational databases, a number of different
approaches were tried. In many cases, these were simple, proprietary data-storage
systems designed around a specific application. However, large corporations, notably
IBM, were marketing more general solutions.
The Relational Model
The big step forward in database technology was the development of the
relational
database model.
The relational database derives from work done in the late 1960s by
E.F. Codd, a mathematician at IBM. His model is based on the mathematics of set
theory and predicate logic. In fact, the term
relational
has its roots in the mathematical
