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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.
each publisher has uniqe name a mial addrs are also kept on each pubisher.a publisher publish one book.a book publish y one publisher.book identified by isbn.each book writn by one
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Define the terms 1) physical schema 2) logical schema. Physical schema: The physical schema explains the database design at the physical level, which is the lowest level of abs
Differentiate between Key and superkey? Key and superkey - A key a single attribute or a combination of two or more attributes of an entity set in which is used to identify o
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Fragmentation: It is definite as partitioning of a relation into various fragments.Every fragment can be stored at a dissimilar site.
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