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Define physical and logical data independence. How does this architecture help in achieving these?
Data independence entails that change in one view must not need a change in the view(s) above. There are two sorts of data independence: logical and physical. The meaning of Logical data independence is that the conceptual view can be changed without influencing the existing external view, that is a given record may be spilt or combined along with other records but the external views need not be modified to reflect this. The meaning of Physical data independence is that the physical storage structures or devices employed to store the data can be changed without effecting the existing conceptual view or external view, that is if earlier indexed sequential files are employed to store data and then the B- trees are used, even then the upper layers must not be effected.
What is meant by object identifiers? Object-oriented systems use an object identifier to recognize objects. Object identifiers are unique: that is every object has a single ide
Explain Object oriented Model ? Object Oriented Model - This model is based on the object-oriented programming language paradigm. It involves the features of OOP such as inhe
During the deletion of a tuple two cases can happen: Deletion of tuple in relation having the foreign key: In this type of case simply delete the desired tuple. For example, in
What are the uses of functional dependencies? To test relations to see whether they are legal under a given set of functional dependencies. To state constraints on the set
what is bogus empowerment. And what is genuine empowerment
1. Staff (staffID --> availabilityID) 2. Services (servicesID --> itemBasedID --> timedBasedID) 3. TimedBased (timedbasedID--> priceid) 4. Clients (clientId, serviceId-->
What is a database? At any given time, they're storing a tremendous amount of information - inventory, in the case of Amazon, messages and interrelationships in the case of Tw
It defines that no primary key value can be null. This is as the primary key is used to recognize individual tuple in the relation. So we will not be able to recognize the records
What are the disadvantages of relational approach? Disadvantages of relational approach: • Substantial hardware and system software overhead • May not fit all business models •
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