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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.
Describe file organisation? A file is organized logically as a sequence of records. These records are mapped onto disk blocks. A) Fixed-Length Records Type deposit=record
Chapter 10a review questions
What is NULL? Simply NULL means not in value.
why are older data models are being replaced by new data models
Consider the relations described below: PHYSICIAN (regno, name, telno, city) PATIENT (pname, street, city) VISIT (pname, regno, date_of_visit, fee) Where the regno and pname ide
Write a Query that uses the UNION Operator 1. Use the Software Experts database to: a. Display the first and the last name of all consultants who worked on any projects f
write short note on mobile database
What subschema expresses ? A subschema expresses the external view. (External schemas are called also called as subschemas)
Partial Key : It is a group of attributes that can uniquely identify small entities and that are related to same base entity. It is sometime named as Discriminator. Altern
The dataset " CFOLYMPICS.XLS " contains the observations used in the above article. The definitions of the variables are also included in this spreadsheet. However, for the purpo
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