Data abstraction
Database system provides an abstract view of the data.
Hide certain complexity details of how data is stored and maintained.
Achieved through several level of abstraction
- Physical level
- Logical level
- View level
Physical level
Physical level describes how a record (e.g. customer) is stored.
Only designers can see.
Logical level
Logical level describes what data are stored in the database, and the relationships among the data .
Logical level describes entire database.
DBAs work at this level of abstraction.
View level
View level describes part of the database.
A way to hide:
- details of data types.
- information (such as an employee’s salary) for security purposes.
Users work at this level of abstraction.
Diagram
