Abstraction of data means “Don’t expose all the data until it has been asked or queried. Hide as much as you can. ” This is one of the main features of database management systems. Hiding irrelevant details from user and providing abstract view of data to users, helps in easy and efficient user-database interaction.
let’s see a real life example, say you wanted to know the the arrival time of a particular flight on a booking site. on the same time another person might be looking for an information regarding departure time of another flight. Here everyone making a query to the company’s database but no one have any knowledge what is going on internally e.g what database they are using, how it is getting connected etc. Everyone just using a presentation layer on their side and get the only results what they are looking for. No one’s results overlapping or no one getting overloaded information than what they had asked.
We have three levels of abstraction:
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.
Logical level: This is the middle level of 3-level data abstraction architecture. It describes what data is stored in database.
View level: Highest level of data abstraction. This level describes the user interaction with database system.
Example: Let’s say 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.
Note: The concept is same as three tier architecture of DBMS.