what is data abstraction in dbms


Ø  Data abstraction – data system are made up of complex data structure the use of data abstraction interaction with database, the use of data abstraction interaction with database the developer hide internal detail from the users.The process of hiding irrelevant detail from user is called data abstraction.

OR
Data abstraction –the main purpose of database system is to provide users with an abstract view of the system the system hide certain detail of how data is store, created and manipulated complexity should be hidden by the database users, which is known as data abstraction.
There are three levels in data abstraction –
1.      Physical level
2.      Logical level
3.      View level


               

1)     Physical level: This is the lowest level of data abstraction. It describes how data is actually stored in database. You can get the complex data structure details at this level.
2)     Logical level: This is the middle level of 3-level data abstraction architecture. It describes what data is stored in database.
3)     View level: Highest level of data abstraction. This level describes the user interaction with database system.
Example:  we are storing customer information in a customer table. At physical level these records can be described as blocks of storage (bytes, gigabytes, etc.) in memory. These details are often hidden from the programmers.
At the logical level these records can be described as fields and attributes along with their data types, their relationship among each other can be logically implemented. The programmers generally work at this level because they are aware of such things about database systems.
At view level, user just interact with system with the help of GUI and enter the details at the screen, they are not aware of how the data is stored and what data is stored; such details are hidden from them.