Data Abstraction in DBMS | What is Data Abstraction in DBMS ?

Data Abstraction is a process of hiding unwanted or irrelevant details from the end user. Data Abstraction can be defined as extracting the necessary data by ignoring the remaining irrelevant details.

If we take the example of a real-world entity, ATM is one of the best examples of data abstraction We all use an ATM machine for cash withdrawal, money transfer, etc in our daily life. But we don't know internally what processes and operations are being performed inside an ATM.

The main purpose of data abstraction is to achieve data independence.

Levels of  Data Abstraction for DBMS:

There are three levels of data abstraction which are as follows: 

• Physical or Internal Level
• Logical or Conceptual Level
• View or External Level

Physical or Internal Level: 

Physical level is the lowest level of data abstraction. It describes how data is actually stored in database. It also describes the data structures and access methods to be used by the database.

Suppose we need to store the details of an employee. Blocks of storage and the amount of memory used for these purposes are kept hidden from the user. 

Logical or Conceptual Level: 

Logical level is the intermediate level or middle level of data abstraction. This level comes between the physical level and view level. It provides the link between the external schema and the internal schema of the database.

 It describes what data are stored in the database and the relationship among those data.

View or External Level:

It is the highest level of data abstraction. This level describes the user interaction with database system. In view level, there are different levels of views and every view only defines a part of the entire data.

This level describes the user interaction with the database management system. It allows user to view the database and do the query. This level is used to provide a Graphical user interface to the user, and the user does not know about the file structure, access method, and other internal details of the database.

Fig: Three Levels of Data Abstraction