Database Reference
In-Depth Information
F
IGURE
1.1
A simple relational database containing employee and computer
information
The Employee table holds all the pertinent data about employees, and
each row in it contains all the information for a single employee. Similarly,
columns
hold the data of the same type for each row. For example, the
PhoneNumber column holds only phone numbers of employees. Many
databases contain other objects, such as views, stored procedures, func-
tions, and constraints, among others; we get into those details later.
Taking the definition one step further, we need to look at relational
databases. A
relational database,
the most common type of database in
use, is one in which the tables relate to one another in some way. Looking
at our Employee table, we might also want to track which computers we
give to which employees. In this case we would have a Computer table that
would relate to the Employee table, as in the statement, “An employee
owns or has a computer.” Once we start talking about relational databases,
we knock other databases off the list. Things like spreadsheets, text files, or
napkins inherently stand alone and cannot be related to other objects.
From this point forward, when we talk about databases, we are referring to
relational databases that contain collections of tables that can relate to one
another.
Relational Database Management Systems
A
relational database management system
(RDBMS) is a software
product that stores relational databases. In addition to storing databases,
RDBMSs provide many other functions. They give you a way to secure the
databases and manage user access. They also have functions that allow you
to manage your databases, functions such as backup and restore, index
management, data loading utilities, and even reporting.
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