RELATIONAL DATABASES.— Relational
databases have many advantages over network and
hierarchical databases. They consist of one or more
tables in which data are stored in the form of rows and
columns. The main advantage is that relationships
between the data can be established whenever you (the
user) request information. For example, relation tables
could be used to link a person with his/her NECs, duty
assignments, and any special qualifications, as shown in
figure 3-10. Many other relations are, of course,
possible. Any relational database package normally
uses an index of some sort for faster access to the data.
Relational structures are a very popular database
structuring approach for both mainframe and
microcomputer database packages.
Using Database Software
Some of the more common operations you can
expect to perform when using a database software
package are as follows:
. Create databases.
. Insert, update, and delete data in a database.
Figure 3-10.—Example of a relational database structure.
l
l
l
l
Create and run forms and reports, design and
print labels.
Query the database for information.
Create and run/execute applications programs.
Import and export files.
You can use function keys F1, F2, and so on, to
provide help screens, to display lists of items, to design
database files, queries, reports, forms, and labels; to add
fields to a layout, to move or copy selected data, to
enlarge/shrink fields or condition boxes, to print a quick
report, to access menus for the current screen, to access
macros, and so on.
Some database packages provide you with some
type of control screen like the one shown in figure 3-11.
Using a control screen allows you to access a number of
features. This particular control screen has six panels,
each corresponding to a different type of operation on
your database.
Displayed across the top left-hand
corner of the control screen you see three main
menus— Catalog, Tools, and Exit. Catalog provides
you with options for managing catalogs and the files
contained in them. A catalog is a file in itself that
contains the names of related files. Tools provide you
with a variety of utilities for accessing the disk
operating system (DOS), for importing and exporting
files, and for setting program parameters. Exit enables
you to leave the control screen and go back to the disk
operating system.
Figure 3-11.—Typical control screen used with database
applications.
3-14
