TABLE OF CONTENTS A database is defined as a collection of stored operational data used by the application systems of some particular enterprise. For instance, a simple filing cabinet or a file system on a computer hard disk can be considered to be databases.
The internal structure of a database is such that data are stored to represent the physical entities [1] of the system, and the relationships that link the entities. These relationships may be represented by pointers, or physical adjacency, and they may be either simple one-to-one relationships, or complex two or three-way relationships. The physical entities possess attributes that describe the features of the entity, each attribute having a domain, or range of permitted values. The way in which the entities, attributes and relationships are represented in the database is dependent on the particular database model used.
The simplest form of computer databases are file systems, where the data are stored in various files, and the access is made through third generation programming languages such as BASIC, COBOL or FORTRAN. Although this method is still used when data are kept in spreadsheets, for instance, keeping data in a file system is equivalent to keeping a computerized list of records. This method has a very large number of disadvantages:
the whole database is searched for a key when the data are needed. This is more or less equivalent to a search/replace procedure in a word processor, i.e., slow;
producing selective reports is extremely...
