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Security: Data not needed by local applications is not stored at the site, therefore no unnecessary security violations may exist.
But how can we carry out fragmentation? Fragmentation may be carried out as per the following rules:
a) Completeness: This rule makes sure that there is no loss of data while fragmentation. If a relation is decomposed into fragments, then every data item must appear in at least single fragment.
b) Reconstruction: This rule makes sure preservation of functional dependencies. It should be possible to describe a relational operation that will reconstruct the relation from its fragments.
c) Disjointness: A data item that shows in a fragment should not show in any other fragment. Though, a typical fragmentation known as vertical fragmentation is an exception to this rule. In vertical fragmentation the primary key attributes must be repeated to permit reconstruction of original relation.
This rule makes sure minimization of data redundancy. What are the dissimilar types of fragmentation?
What are the uses of the information in the Data dictionary? The following information is directly taken from the Data dictionary: Information on fields displayed with
Define a property that is not a property of transactions? Ans: Concurrency is not a property of transactions
When It is better to use files than a DBMS? It is better to use files than a DBMS when Multiple users wish to access the data.
what is er digram given that example of hospital,bank and library er digram.
Due date for May 8
Retrieve the S&S In-Chapter Database (in Microsoft Access format) from the text's Web site (or create the tables in Table 4-5 in a relational DBMS product). Write queries to answer
Replicating Data One approach that may support efficient access to dissimilar applications as above may be to give access to every of the applications from dissimilar replicate
Can we delete data element, which is being used by table fields. No we cant delete data element.
Define what Immediate database modification technique uses? Ans: Both undo and redo.
Key to represent relationship amongs tables is called ? A Key that represent the relationship between tables is called Foreign Key.
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