The Databases

A database is a way of storing large quantities of information so that, using a computer, it can be

1. searched: to find specific data.

2. sorted (i.e, organised in different ways): to compare data and create reports.

Databases have become essential in many different areas of modern life from government and business to science and education. Tax authorities, for example, use databases to keep records of taxpayers and payments, businesses use them to keep customer account and schools use them to maintain student records.

A simple flat-file database is like a table with vertical columns, called 'fields', and horizontal rows, called 'records'. The records refer to the people or things with which the database is concerned (students, customers, products, etc.) and the fields contain various categories of information about them.

Fields can consist of different types of data: Text: for example names or brief descriptions (codes, such as M/F for male/female, are often used to save space). Dates or times: which must follow a standardised format (e.g, 18/09/02). Numberst which may be integers (whole numbers: 6) or decimal numbers (6, 5). Calculated numbers: which are automatically worked out using a formula (e.g, a person's age based on their date of birth + today's date) Graphics: which may be a photograph or any other type of image.

A flat-file database enables a user to view data from only one file at a time. A relational database is a more complex system in which data from many different files are interlinked. In this case a database management system (DBMS) is necessaryto organise and analyse all this data. A programming language, called "Structured Query Language" (SQL), enables users to define the sort of data they are looking for. For example, a shopping website uses SQL to translate a customer's input into a request for the DBMS. The DBMS then instructs the computer to retrieve the data that match the definition requested.