Database Reference
In-Depth Information
well. If companies did not need more and newer types of information, there would
have been no impetus for development of database systems. The earlier data systems
might have been satisfactory.
Inadequacy of Earlier Data Systems.
Suppose the earlier data systems were able
to meet the escalating demand for information. Then why bother to find better
methods? But the fact is that these earlier systems were grossly inadequate to meet
the information demands. Storage and management of large volumes of data were
not adequate. Finding and retrieving information were extremely difficult. Protect-
ing the information asset of a company was nearly impossible with the earlier data
systems. Why was this so? How were the earlier systems inadequate? In what ways
could they not meet the information demands? Understanding the limitations will
give you a better appreciation for database systems.
Inadequacy of Earlier Data Systems
Assume that you work for a company called Progressive Book Distributors in
the early 1970s. Your company purchases topics from various publishers and sells
them to retail bookstores and book clubs. The computer applications in your
company would work with sequential files because those are the types of data
systems available at that time. Here is a list of possible sequential computer files in
your company.
Customer master file
Every time a new customer comes on board, a record is
created in the file, with a new customer number, in the order in which the cus-
tomers are added.
Book master file
As each new book is added to the inventory, a record is created
in the file, with ISBN identifying each book.
Salesperson file
As each new salesperson is hired, the person is given an iden-
tification number and data about him or her is added to the file.
Sale transaction file
Each sale is recorded with the date of the sale.
Publisher file
As each new publisher is included, a record is created in the file,
with a new publisher number, in the order in which the publishers are added.
Payment transaction file
Payments received from customers are recorded with
the date of the payment.
Refer to Figure 1-4 showing the fields and sample data for each file.
What types of information is your company's staff looking for? Do they need to
print an invoice for customer Allbooks Book Store for the sale on January 10, 2002?
Do they want the total sales of all topics from publishers Ron Fairchild during the
month of December 2001? Do they want a list of all customers in New York state?
In today's computing environment, no one will think of these requests as difficult
or impossible. This was not the case with file-oriented applications of the early 1970s.
File-oriented data systems have serious limitations.
Let us take just one specific example of printing statements to customers for sales.
This had to be done in a batch mode at the end of a reasonable interval such as at
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