Progress
Database Design
Guide
What Is a Database?
A database is a collection of data that you can search through in a systematic way to maintain and retrieve information. A database can be computerized or noncomputerized. Some noncomputerized databases that you’re familiar with are a telephone book, a filing cabinet, and a library card catalog system. To retrieve information from each of these databases, you proceed accordingly:
- To look up a friend’s phone number, you thumb through the telephone book of the town they live in, and search for their last name, followed by their first name. If there is more than one occurrence of the name, you check the addresses, and by process of elimination, you determine your friend’s phone number. The telephone book has a very simple and restricted structure. You cannot, for instance, look up a phone number by the person’s first name or by their address.
- To check the balance on a customer’s account, you rifle through a filing cabinet to locate the customer’s folder and pull out the piece of paper with the current balance on it. This database, too, has a restricted structure. You cannot, for instance, look up a customer’s record by their address or the name of their sales representative. Furthermore, to look up all customers with an outstanding balance of more than $1,000, you must go through all the folders individually to find the customers that meet this criteria.
- To find a book in the library, you must first determine whether the library has the book by looking it up in the card catalogs, either by title, author’s name, or subject matter. You note its decimal ID number, then go to the appropriate shelf and locate the book. Of the three databases, the card catalog is the most sophisticated because it allows you to look up a book in at least three different ways.
To summarize, if you want to locate information quickly and effortlessly in each of these noncomputerized databases, you must store every piece of data—name, customer folder, or catalog card—in some sort of order. Even then, it can take anywhere from a few minutes to several hours to locate the data, depending on the size of your database and the complexity of the query.
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