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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.
For each m:n relationship type R, we make a new table (say S) to represent R. We also contain the primary key attributes of both the participating entity types as a foreign key att
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You are to write a property management database program that allows a real estate agent to view, add, search, and save property listings. The program is to do the following: 1.
a need some real life examples of database management systems three level of ANSI SPARC architecture life teacher and student ,company and employee or for NGO etc.
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What are partial, alternate,, artificial, compound and natural key? Partial Key: It is a set of attributes that can uniquely recognize weak entities and that are related to s
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Prove that a relation which is 4NF must be BCNF. Ans Let R be in 4NF. Suppose it is not in BCNF. Hence, there exists an FD X→Y in R such that x is not a super key. Although
What are the two approaches to store relations in distributed database? a) Replication b) Fragmentation
This project requires you to create a database design. Your design will be documented in a set of Entity-Relationship diagrams. Draw a set of Entity-Relationship diagrams to mode
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