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Differentiate between various levels of data abstraction?
Data Abstraction - Abstraction is the procedure to hide the irrelevant things from the users and represent the relevant things to the user. Database systems are frequent used through non-computer professionals so in which the complexity must be hidden from database system users. This is done through defining levels of abstract as that the database may be viewed; there is logical view or external view, conceptual view and internal view or physical view.
1. External View - This is the highest level of abstraction as seen through a user. It describes only the part of whole database, that is relevant to a particular user.
2. Conceptual View - This is the next higher stages of abstraction that is the sum total of Database Management System user's views. It elaborates what data are in fact stored in the database. It contains information about whole database in terms of a small number of associatively easy structure.
3. Internal View - This is the lowest level of abstraction. It elaborates how the data are physically stored
Problem Explain at least five relational algebraic operators with a suitable example. Note: All the above descriptions should be done by taking at least two examples from ou
explain equi-join using illustration
It can be easily defined as: The database must not have any unmatched foreign key values. The term "unmatched foreign key value" means a foreign key value for which there doe
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Which operation is used if we are interested in only certain columns of a table? PROJECTION operation is used if we are interested in only certain columns of a table.
wh
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I am doing research in this area, especially in sime join and join efficacy when several relations have been queried. Relations located in different sites. I need something like n
OBJECTIVES After going through this unit you should be capable to: Explain the File Based system and its limitations; Explain the structure of DBMS; Explain the
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