Describe the three levels of data abstraction?
The are three levels of abstraction:Ø Physical level: The lowest level of abstraction describes how data are stored.Ø Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data.Ø View level: The highest level of abstraction describes only part of entire database.7. Define the “integrity rules”There are two Integrity rules.Ø Entity Integrity: States that “Primary key cannot have NULL value”Ø Referential Integrity: States that “Foreign Key can be either a NULL value or should be Primary Key value of other relation.
The are three levels of abstraction: Ø Physical level: The lowest level of abstraction describes how data are stored. Ø Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data. Ø View level: The highest level of abstraction describes only part of entire database.
The are three levels of abstraction: Physical level: The lowest level of abstraction describes how data are stored. Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data. View level: The highest level of abstraction describes only part of entire database.
