Introduction to Database
Introduction to Database: A database is a collection of related data that must be stored in an efficient and compact manner. The word “efficient” means that stored data can be accessed very easily and quickly that must be efficient. Similarly, the word “compact” means that the stored data takes up as little space as possible.
A database holds related data as well as a description of data. For this reason, a database is also defined as a self-describing collection of integrated records. The description of stored data is known as the system catalog or data dictionary or metadata.
A database may be generated and maintained manually or it may be computerized in a system. The library card catalog is one of the common examples of a database that is created and maintained manually. On the other hand, a computerized database may be created and maintained either by using an application program, which is developed specifically for that purpose or by a database management system.
Types of Databases
The databases may be different types but there are two generic types of database architectures. These are
- Centralized Databases
- Distributed Databases
Centralized Databases
A database whose complete data is located at a single computer (called database server) and all the users access this single database only, is known as the Centralized Database. A centralized database provides an efficient way to access and update data. These databases are manually used in computer network environments.
The example of the centralized database are:
(i) Personal Database
(ii) Central Database
(i) Personal Database
A personal database is normally created and maintained by a single user on his personal computer. The personal computer databases are commonly used in small business organizations. The personal computer databases are used for simple accounting, inventory management, and customer billing system, etc. These are relatively simple to develop and use. The main problem with the personal computer database is that the data can not easily be shared among different users.
(ii) Central Database
The central database is generally used in the organization where no security or proper authentication of the user is needed. One of the computers in the network is selected to host the database, which is created using MS-Access etc. Other users in the network freely access this database without any authentication through any server computer.
Distributed Database
Many organizations\department have sub-office in different cities and countries. In such a case, the distributed database is used instead of centralized databases. A distributed database is a logical database, which is spread physically across multiple computers (called database server) over wide area network. Such a database is managed by the organizations having offices in different cities and countries.
