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

Construct substantial data model, PART MARKING:  We will only mark TWO of t...

PART MARKING:  We will only mark TWO of the four questions below but you must submit answers to all four. We will choose the questions we mark randomly and we will supply you with

Creating database for library, i need help with creating database system fo...

i need help with creating database system for a library

Method of analyzing association traversal, Analyzing Association Traversal ...

Analyzing Association Traversal Till now, we have supposed that associations are bi-directional. But in the case of traversal, it is in only one direction in any application,

FIELDS, 4. Describe three ways to handle missing field values

4. Describe three ways to handle missing field values

Database problem in wordpress, Project Description: I am having a random...

Project Description: I am having a random problem with my Wordpress site. If I click on "Publish" and "Add new", it takes me to a 404 page not found of /wp-admin/post.php (th

Explain the concept of deadlock, Question: In a multi-user database env...

Question: In a multi-user database environment, locking mechanisms can be used to solve the three basic problems of concurrency. On the other hand, however, locking may also le

What is predictive modelling, Question : (a) Data mining is one of the...

Question : (a) Data mining is one of the best ways to analyse data and using software method, hidden and unexpected patterns and relationships in sets of data can be extracte

Example of transaction? , Example :; transfers transfer_amount from x's acc...

Example :; transfers transfer_amount from x's account to y's account ; Supposes x&y both accounts exist TRANSACTION (x, y, transfer_amount) Start transaction IF X AND Y

Extended star schema model, A customer places orders for parts and belongs ...

A customer places orders for parts and belongs to a particular industry group. An individual order is taken by a particular sales representative on a specific date and the sales re

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