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Data Abstraction is a process of hiding unwanted or irrelevant details from the end user. It provides a different view and helps in achieving data independence which is used to enhance the security of data.
Mainly there are three levels of abstraction for DBMS, which are as follows −
1. Physical or Internal Level:
It is the lowest level of abstraction for DBMS which defines how the data is actually stored, it defines data structures to store data and access methods used by the database. Actually, it is decided by developers or database application programmers how to store the data in the database.
So, overall, the entire database is described on this level that is physical or internal level. It is a very complex level to understand. For example, customer information is stored in tables, and data is stored in the form of blocks of storage such as bytes, gigabytes, etc.
2. Logical or Conceptual Level:
The logical level is the intermediate level or the next higher level. It describes what data is stored in the database and what relationship exists among those data. It tries to describe the entire or whole data because it describes what tables are to be created and what are the links among those tables that are created.
It is less complex than the physical level. The logical level is used by developers or database administrators (DBA). So, overall, the logical level contains tables (fields and attributes) and relationships among table attributes.
3. View or External Level:
It is the highest level. At the view level, there are different levels of views and every view only defines a part of the entire data. It also simplifies interaction with the user and it provides many views or multiple views of the same database.
View level can be used by all users (all levels’ users). This level is the least complex and easy to understand.
For example, a user can interact with a system using GUI that is view level and can enter details at GUI or screen and the user does not know how data is stored and what data is stored, this detail is hidden from the user.
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