Delete - referential integrity, Database Management System

Assignment Help:

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.


Related Discussions:- Delete - referential integrity

Describe object relational model, Describe Object Relational model ? O...

Describe Object Relational model ? Object Relational Model - This model combines the characteristics of both relational model and object oriented model. It extends the tradit

Relational constraints, Relational and E-R Model There are three types o...

Relational and E-R Model There are three types of constraints on relational database that have: DOMAIN CONSTRAINT PRIMARY KEY CONSTRAINT INTEGRITY CONSTRAINT

Implement a cache simulator, You are required to program (in a high level l...

You are required to program (in a high level language such as C, C++, Java) and implement a cache simulator which will have the following inputs and outputs:- INPUTS

Explain concurrency problems, Question: a) There are three concurrency...

Question: a) There are three concurrency problems, i.e. three types of potential mistake which could occur if concurrency control is not properly enforced in the database syst

What is a sub-query, (a) What is a Sub-Query? (b) What is the differen...

(a) What is a Sub-Query? (b) What is the difference between a scalar sub-query and a tabular sub-query? (c) Write an equivalent SQL statement to get the Name of Product wh

Define the concept of design documentation, Design Documentation  The ...

Design Documentation  The Design Document shall be an extension of Requirements Analysis Design. "The Design Document will comprise a revised and much more detailed descrip

Which model is record based logical model, Which model is record based logi...

Which model is record based logical model? Network Modelis basically known as record based logical model.

Information system fundamentals, A full discription of the new, a discripti...

A full discription of the new, a discription of its components, and the bebefit it will provide a company. A disscussion of the information usedin the system. A disscussion of any

What is an operand, What is an Operand? The data on which the operation...

What is an Operand? The data on which the operation is to be performed is known as an Operand

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd