Database Introduction

A database is a collection of related data and the database management system is the software that manages and controls access to the database. Database is a collection of data (information) on a specific topic stored in an organized manner. In other words, a database is a collection of logically related data, designed to meet the information needs of an organization. Consider example #1: Whenever you visit your local library, there is probably a database containing details of the books in the library, details of the users, reservations and so on. There will be a computerized index, which allows users to find a book based on its title, or its authors or its subject area. The database system will handle reservations to allow a user to reserve a book and to be informed by post when the book is available. The system will also send out reminders to borrowers who have failed to return books on the due date. Typically the system will have a bar code reader, which is used to keep track of books coming in and going out of the library. Consider example #2: When you purchase goods using your credit card, the assistant normally checks that you have sufficient credit left to make the purchase. This check may be carried out by telephone or a card reader linked to a computer system may do it automatically. In either case, there is a database somewhere that contains information about the purchases you have made using your credit card. To check your credit, there is an application program that uses your credit card number to check that the price of the good you wish to buy together with the sum of the purchases you have already made this month is within your credit limit. When the purchase is confirmed, the details of the purchase are added to this database. The application program will also access the database to check that the credit card is not on the list of stolen or lost cards before authorizing the purchase. There will be other application programs to send out monthly statements to each cardholder and to credit accounts when payment is received. Consider example #3: If you are at a University, there will be a database system containing information about yourself, the course you are enrolled in, details about your grant, the modules you have taken in previous years or are taking this year, and details of all your past examination results. There may also be a database containing details related to the next year’s admissions and a database containing details of the staff that work at the university, giving personal details and salary-related details for the payroll office.

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