Database Abstraction
A major purpose of a database is to provide the user with only as much information as is required of them. This means that the system does not disclose all the details of the data, rather it hides some details of how the data is stored and maintained. The complexity of databases is hidden from them which, if necessary, are ordered through multiple levels of abstraction to facilitate their interaction with the system. The different levels of the database are implemented through three layers:
- Internal Level(Physical Level): The lowest level of abstraction, the internal level, is closest to physical storage. It describes how the data is stored concretely on the storage medium.
- Conceptual Level: This level of abstraction describes what data is concretely stored in the database. It also describes the relationships that exist between the data. At this level, databases are described logically in terms of simple data structures. Users at this level are not concerned with how these logical data structures will be implemented at the physical level.
- External Level(View Level): It is the level closest to users and is related to the way the data is viewed by individual users.
Data Abstraction
Since a database can be viewed through three levels of abstraction, any change at one level can affect plans at other levels. As databases continue to grow, there may be frequent changes to it at times. This should not lead to redesign and re-implementation of the database. In such a context the concept of data independence proves beneficial.
Basic Database Concepts
The database system is an excellent computer-based record-keeping system. A collection of data, commonly called a database, contains information about a particular enterprise. It maintains any information that may be necessary to the decision-making process involved in the management of that organization. It can also be defined as a collection of interrelated data stored together to serve multiple applications, the data is stored so that it is independent of programs that use the data. A generic and controlled approach is used to add new data and modify and retrieve existing data within the database. The data is structured so as to provide the basis for future application development.