In a database management system (DBMS), there are three levels of abstraction that allow users to interact with the database at different levels of complexity. These levels are:
Physical level: The physical level is the lowest level of abstraction, and deals with the physical storage and organization of data on the storage devices. It involves specifying how data is stored on disk, including details such as data blocks, record formats, and access methods. Users at this level interact with the data in terms of bits, bytes, and physical storage locations.
Logical level: The logical level is the next level of abstraction, and deals with the logical structure of the data. It involves specifying the entities, attributes, and relationships between the different data elements in the database. Users at this level interact with the data in terms of tables, views, and relationships.
View level: The view level is the highest level of abstraction, and deals with the way data is presented to the end users. It involves specifying how data is organized and presented to users, including queries, forms, and reports. Users at this level interact with the data in terms of meaningful business concepts, such as customers, orders, and products.
Each level of abstraction builds on the level below it, and provides a higher level of abstraction and a simpler view of the data. This allows users at different levels to interact with the data in a way that is most appropriate for their needs, without having to deal with the complexity of the lower levels. The levels of abstraction also provide a separation of concerns, allowing different groups of users to work on different aspects of the database without interfering with each other. This makes it easier to develop, maintain, and evolve the database over time.
