the database for the records that meet the criteria (SKI
or SK2, Supply Department, and NEC 1234). The
computer then displays or prints the requested
information in the format specified. See figure 3-6. You
do this through the query and report features of the
database package. Doesnt that beat manually searching
through a drawer full of folders, which could take
A database is nothing more than a collection of
datamany file folders or individual records
containing several fields or data elements. The database
is organized to allow you to retrieve, update, and have
ready access to various information that can be
formatted and printed as you desire. The database itself
doesnt do anything; it just holds information.
Understanding Database Software
To understand how a database program works, you
first need to have an understanding of certain terms.
Some of the terms you are already familiar with,
whereas others you may not be. These include
database, record, field, pointer, index, primary key,
and secondary key. They are defined as follows:
. Database A database holds information that is
related to a specific type of application-payroll,
personnel, supply inventory, and so on. In this
context, the term database is often considered
synonymous with file. This is especially true
when dealing with database files.
l Record A record consists of a group of related
fields, all pertaining to the same subject: a
person, a thing, or an event.
Figure 3-6.Example of a database report.
Field A field consists of one unit of
information. A field is also referred to as a data
item or a data element. It maybe alphabetic, like
your name (John or Jane Doe); numeric, like
your ZIP Code (01234); alphanumeric, like your
post office box or street address (P. O. Box 669 or
1234 Main St.); or logical (true/false), like on
leave (true-on leave, false-not on leave).
Pointer A pointer is a data item in one record
that identifies the storage location of another
logically related record.
Index An index enables you to access records
in a database (also referred to as database file or
file) in the order of the index regardless of the
physical sequence of the records in the database.
You can think of indexing as sorting without
having to sort.
The index itself is a file. It
contains a duplicate of the key field (or fields)
such as account number, or name and security
number, and a pointer to the actual disk record
identified with this key in another permanent
disk file. For example, if there are 5,000 records
in your database, and the key field happens to be
SSN, then the index would also contain 5,000
entries with each entry having an SSN. It is also
possible for you to have one or more secondary
indexes that contain other various secondary key
Primary key The primary key in a database
consists of a unique identifier for a particular
record and should only point to a single record in
the database being indexed.
Secondary key Data are normally arranged
within a database in some type- of order,
depending upon the contents of one or more
fields. Secondary keys allow you to access the
database in different ways. For example, your
database might be arranged in the order the
records were entered. You can then set up a
secondary index (or key) by the name field, or by
the social security number field. You may
specify any number of secondary keys. You
might index by more than one field. For
example, you could index by last name within
rate, as shown in figure 3-6.
Database Organization Methods/Structures
Databases can be list, hierarchical, network, or
relational in structure.
The major advantage of a