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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.
Oracle & Distributed Databases 1. Differentiate between PL/SQL functions and procedures. 2. Draw the diagram of logical structure of oracle database and explain it in brief.
Consider employee (e_no, e_name, e_salary, d_code), dept (d_code, d_name) and dependent (depndt_name, e_no, relation). Show the names of employees in purchase and accounts departm
a. Define the term "deadlock". There are four conditions that must hold before deadlock is possible. Name them. b. Outline an algorithm that detects whether there is a deadlock.
Control Files : The redo and control files logs support the rest of the architecture. Every database must have at least one control file, although you have more than one to guard
What is Stored Procedure? A stored procedure is a named group of SQL statements that have been previously formed and kept in the server database. Stored procedures accept input
how to operate database in access ?
What is property - properties of a database ? It is an integrated collection of logically related records. It consolidates separate files into a common pool of data records and
Sequential File Organisation The most necessary way to organise the collection of records in a file is to use sequential Organisation. Records of the file are stored in series
Consider the entity type dependent related to employee entity, which is used to keep track of the dependents of every employee. The attributes of dependents are: name, sex, birth d
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