A database is a collection of related files. It is also defined as a group of stored, integrated (cross-referenced) data elements that can be retrieved and manipulated with great flexibility to produce information. A database management system (DBMS) is a computer-based system whose software allows creation, maintenance, and manipulation of a database to produce relevant business or research information. By integrated we mean that the file records are logically related to one another so that all data on a topic can be retrieved by simple requests. The database management system software represents the interface among the user, the operating system and the database.
For example, suppose you need to review the customer files for all invoices for payments due in excess of $2500 and prepare a simple report. How would probably go through the customer files in alphabetical order, folder by folder. You would examine each invoice in the folders to determine if the amount is in excess of $2500 and remove and copy each invoice that meets the criterion. You would them have to retile the copies you removed (and risk misfiling them). When you had examined all the customer folders and copied all the appropriate invoices, then you would review the copies and put together your report. Imagine how much time this could take. If there are a lot of customers, you need to waste hours if not days.
Now let’s look at the situation in a different way. The environment is the same, except you have, instead of file cabinets, a microcomputer or a terminal and DBMS software that has access to a customer database file. In this file a row of customer data is referred to as a record. An individual piece of data within a record, like a name is referred to as a field. To get the invoice data you need, ou would do something like this:
-Turn on the computer and the printer.
-Start up the DBMS software.
-Give the command to “open up” the customer database file stored on your disk which is same concept to manually opening up the customer drawer in a file cabinet.
-Give the command to search all the records in the database file and display copies of the records that meet your criterion (that is, the names of people with unpaid invoices greater than $2500). If you were using dBASE IV, popular microcomputer DBMS(database management system), the command would look something like:
LIST FOR_INV AMOUNT > 2500
Data Management Short Concepts: The DBMS approach to storing and retrieving data in computer-usable form has evolved to allow users to easily retrieve and updata data that is in more than one file. To explain the DBMS approach and its significance, we will first describe the traditional system it evolved from-the file management system.