January 28, 2020
Amitraj
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 3 levels in data abstraction:-
1. Physical level
2. Logical level
3. view level
1. Physical Level - The lowest level of abstraction describes how the data are actually stored. The physical level describes complex low-level data structures in detail.
2. Logical Level - This is the middle level of 3-level data abstraction architecture. The next-higher level of abstraction describes what data are stored in the database, and what relationships exist among those data.
3. View Level - The highest level of abstraction describes only part of the entire database. 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, terabytes 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.
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 3 levels in data abstraction:-
1. Physical level
2. Logical level
3. view level
1. Physical Level - The lowest level of abstraction describes how the data are actually stored. The physical level describes complex low-level data structures in detail.
2. Logical Level - This is the middle level of 3-level data abstraction architecture. The next-higher level of abstraction describes what data are stored in the database, and what relationships exist among those data.
3. View Level - The highest level of abstraction describes only part of the entire database. 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, terabytes 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.
