Can you think of a business that doesnât have a database that is stored on a computer? Itâs hard. I do know of one, however. It is a small used paperback bookstore. A customer brings in used paperbacks and receives credit for them based on the condition, and in some cases, the subject matter, of the books. That credit can be applied to purchasing books from the store at approximately twice what the store pays to acquire the books. The books are shelved by general type (for example, mystery, romance, and non-fiction), but otherwise not organized. The store doesnât have a precise inventory of what is on its shelves.
To keep track of customer credits, the store has a 4 Ă 6 card for each customer on which employees write a date and an amount of credit. The credit amount is incremented or decremented based on a customerâs transactions. The cards themselves are stored in two long steel drawers that sit on a counter. (The cabinet from which the drawers were taken is nowhere in evidence.) Sales slips are written by hand and cash is kept in a drawer. (Credit card transactions are processed by a stand-alone terminal that uses a phone line to dial up the processing bank for card approval.) The business is small, and its system seems to work, but it certainly is an exception.
Although the bookstore just described doesnât have a computer or a database, it does have data. In fact, like a majority of businesses today, it relies on data as the foundation of what it does. The bookstoreâs operations require the customer credit data; it couldnât function without it.
Data form the basis of just about everything an organization that deals with money does. (It is possible to operate a business using bartering and not keep any data, but that certainly is a rarity.) Even a Girl Scout troop selling cookies must store and manipulate data. The troop needs to keep track of how many boxes of each type of cookie have been ordered, and by whom. They also need to manage data about money: payments received, payments owed, amount kept by the troop, amount sent to the national organization. The data may be kept on paper, but they still exist and manipulation of those data is central to the groupâs functioning.
In fact, just about the only âbusinessâ that doesnât deal with data is a lemonade stand that gets its supplies from Momâs kitchen and never has to pay Mom back. The kids take the entire gross income of the lemonade stand without worrying about how much is profit.
Data have always been part of businesses.1 Until the mid-twentieth century, those data were processed manually. Because they were stored on paper, retrieving data was difficult, especially if the volume of data was large. In addition, paper documents tended to deteriorate with age, go up in smoke, or become water-logged. Computers changed that picture significantly, making it possible to store data in much less space than before, to retrieve data more easily, and usually to store it more permanently.
The downside to the change to automated data storage and retrieval was the need for at some specialized knowledge on the part of those who set up the computer systems. In addition, it costs more to purchase the equipment needed for electronic data manipulation than it does to purchase some file folders and file cabinets. Nonetheless, the ease of data access and manipulation that computing has brought to businesses has outweighed most other considerations.
Defining a Database
Nearly 35 years ago, when I first started working with databases, I would begin a college course I was teaching in database management with the following sentence: âThere is no term more misunderstood and misused in all of business computing than âdatabase.â â Unfortunately, that is still true to some extent, and we can still lay much of the blame on commercial software developers. In this section, we will explore why that is so, and provide a complete definition for a database.
Lists and Files
A portion of the data used in a business is represented by lists of things. For example, most of us have a contact list that contains names, addresses, and phone numbers. Business people also commonly work with planners that list appointments. In our daily lives, we have shopping lists of all kinds as well as âto doâ lists. For many years, we handled these lists manually, using paper, day planners, and a pen. It made sense to many people to migrate these lists from paper to their PCs.
Software that helps us maintain simple lists stores those lists in files, generally one list per physical file. The software that manages the list typically lets you create a form for data entry, provides a method of querying the data based on logical criteria, and lets you design output formats. List management software can be found not only on desktop and laptop computers, but also on our handheld computing devices.
Unfortunately, list management software has been marketed under the name âdatabaseâ since the advent of PCs. People have therefore come to think of anything that stores and manipulates data as database software. Nonetheless, a list handled by list-management software is not a database.
Databases
There is a fundamental concept behind all databases: There are things in a business environment about which we need to store data, and those things are related to one another in a variety of ways. In fact, to be considered a database, the place where data are stored must contain not only the data but also information about the relationships between those data. We might, for example, need to relate our customers to the orders they place with us and our inventory items to orders for those items.
The idea behind a database is that the userâeither a person working interactively or an application programâhas no need to worry about the way in which data are physically stored on disk. The user phrases data manipulation requests in terms of data relationships. A piece of software known as a database managem...