Database systems consists of complex data structures. To make the user interaction easy with the database, developers hide the internal irrelevant details from the users. This process of hiding the internal irrelevant details from the user is known as data abstraction. This is divided into 3 levels of abstraction in DBMS.
Levels of Abstraction in DBMS
These levels are also known as schemas.
There are three levels of abstraction in Database Management System
- Physical/internal level
- Logical/conceptual level
- External level/ view
Internal level is the lowest schema in the levels of abstraction in DBMS. It defines the physical storage structure of a database. Also helps to keep information about the representation of a database. This internal schema shows how and which data is stored in a database. This level never deals with physical devices.
Conceptual level is the intermediate or middle level in data abstraction of DBMS. This describes the Database structure of the whole database for a set of users. This level hides the information about the physical storage structures and focuses on describing the entities, relationships, data types etc…
There is only one conceptual/logical level in one database. Logical schema is in between physical schema and external schema. In a conceptual level, all the data available to the user must be either present in the physical schema or derived from the physical schema.
External level or view level is the highest level in the DBMS levels of abstraction. It describes a part of database in which specific user is interested in. This hides the irrelevant details from the user. It is the content of a database as seen by a specific user. An external schema can have any number of external views for a database.
Advantages Database Schema
- More secured as the user doesn’t have direct access to database.
- We can make changes on external level without effecting the other two levels.
- Data independent to physical storage can be managed.
- As all the levels are separate we can use different developers for each level.
- Fast migration to new graphical environment.
Disadvantages of Database Schema
- Difficult to understand as the database schema is complex.
- Physical separation of the levels can affect the performance of a database.
- Setup and maintenance are difficult.
Reference: Database Management Systems
How many levels of abstraction in DBMS?
There are 3 levels of abstraction in Database Management System.
What are different levels of abstraction in DBMS?
The three levels of abstraction in DBMS are