Data Abstraction

It is the process of removing some characteristics from something to make that particular set with essential characteristics. It gives us a simplified representation of the data.

Data abstraction is the programming process of creating a data type, usually a class, that hides the details of the data representation to make the data type easier to work with. 

PHYSICAL LEVEL-  This is the lowest level of abstraction that describes how data are stored. 

LOGICAL LEVEL-  This is the next higher level of abstraction that describes what data are stored in the database and how they are interrelated. The logical level thus describes the entire database in terms of a small number of relatively simple structures. Database administrators, who must decide what information to be kept in the database use this level of abstraction.

VIEW LEVEL- This is the highest level of abstraction that describes only one part of the entire database. Many users of the database system do not need all such information; instead, they need to access only a part of the database. The view level of the abstraction exists to simplify their interaction with the system  

The Three Levels Of Abstraction  

For example, we may describe a record as follows:

type instructor = record 

                     ID : char(5);

                     name : char(5);

                     dept_name : char(20);

                     salary : numeric (8,2);

                  end;

This code defines a new record type called instructor with four fields. Each field has a name and a type associated with it.