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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 ASSIGNMENT relation we can simply delete the first tuple.
Deletion of the target of a foreign key reference: For instance, an attempt to delete an employee tuple in EMPLOYEE relation whose EMPID is 101. This employee shown not only in the EMPLOYEE but also in the ASSIGNMENT relation. Can these tuple be deleted? If we delete the tuple in EMPLOYEE relation then two unequalled tuples are left in the ASSIGNMENT relation, therefore causing violation of referential integrity constraint. Therefore, the following two choices be for such deletion:
RESTRICT - The delete operation is "restricted" to only the situation where there are no such matching tuples. For instance, we can delete the EMPLOYEE record of EMPID 103 as there is no matching tuple in ASSIGNMENT but not the record of EMPID 101.
CASCADE - The delete operation "cascades" to delete also those matching tuple. For instance, if the delete mode is CASCADE then deleting employee having
EMPID as 101 from EMPLOYEE relation will also make deletion of 2 more tuples from ASSIGNMENT relation.
Explain how you can define an object model of a system. A list of terms that shall be used by end users to describe state and behaviour of objects in system. Different use
a set of possible data value of an attribute is called??
i am not clear with the climetic condition of the north indian plain. can u plz explain it for me
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What is a primary index? A primary index is an index whose search key also explains the sequential order of the file.
, write the relational schema, and draw the new dependency diagrams. Identify the normal forms for each table structure you created
Define Physical and Logical independence Ans: Physical data independence: The ability to modify physical level without causing application program to be rewritten. Logic
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