Dealing with constraints violation, Database Management System

Assignment Help:

If the deletion violates referential integrity constraint, then three alternatives are available:

  • Default option: - refuse the deletion. It is the job of the DBMS to describe to the user why the deletion was rejected.
  • Attempt to propagate (or cascade) the deletion by deleting tuples that reference the tuple that is being deleted.
  • Vary the value of referencing attribute that origins the violation.

Example:

Let R:

A#

B

C^

A1

B1

C1

A2

B3

C3

A3

B4

C3

A4

B1

C5

Q

C#

D

C1

D1

C3

D2

C5

D3

 

 

 

Note:

1) '#' shows the Primary key of a relation.

2) '^' shows the Foreign key of a relation.

(1) Delete a tuple with C# = 'C1' in Q.

Violated constraint: - Referential Integrity constraint

Motive: - Tuples in relation A refer to tuple in Q.

Dealing: - Options available are

1)  Decline the deletion.

2)  DBMS may automatically delete all tuples from relation S and Q with C

# = 'C1'. This is known as cascade detection.

3)  The one more option would result in putting NULL value in R where C1 exist, which is the initial tuple R in the attribute C.


Related Discussions:- Dealing with constraints violation

Incident report to the database, The Form input elements are:           ...

The Form input elements are:             Reporter name                                                text type input             Password

What are advantages of object-oriented programming paradigm, What is the ma...

What is the major advantage of object-oriented programming paradigm? The ability to modify the explanation of an object without affecting the rest of the system is the main adv

What is an object design, What is an object design? Object design is a ...

What is an object design? Object design is a very interactive method, which decides the relationship among objects, classifies operations on classes, determines overall system

Attributes, Attributes and its types explain?

Attributes and its types explain?

Define database management system, Define database management system? D...

Define database management system? Database management system (DBMS) is a set of interrelated data and a combination of programs to access those data.

What is data model, A Data Model in software engineering is an abstract...

A Data Model in software engineering is an abstract model that organizes and documents the business data for interaction between team members and is used as a plan for creating

Database design in third normal form, The following data are required to be...

The following data are required to be stored by a family physician. Family#, FamilyAddress, Patient#, PatientName, ServiceCode, ServiceFee, ServiceDate A family can have seve

Define the immediate update, Define the Immediate Update The immediate...

Define the Immediate Update The immediate update methods may apply changes to the database on disk before the transaction arrives a successful conclusion. Though, these change

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