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

Example of sequences, Example : Create a sequence named SEQSS that starts a...

Example : Create a sequence named SEQSS that starts at 105, has a step of 1 and can take maximum value as 2000.  CREATE SEQUENCE SEQSS START WITH 105 INCREMENT BY 1 MAX VA

What are the three types of data sources, What are the three types of data ...

What are the three types of data sources used with ODBC? An ODBC file data source is a file that can be shared between database users. An ODBC system data source is one that is

Eliminate repeating groups, Eliminate Repeating Groups The problem is, ...

Eliminate Repeating Groups The problem is, "Find out the list of employees, who knows DB2". For this problem we require to perform an awkward scan of the list looking for re

Describe the host language, Describe the host language? Host Language:...

Describe the host language? Host Language: You could write applications along with SQL statements embedded inside a host language. The SQL statements give the database inter

Log, what is the need of a log in dbms

what is the need of a log in dbms

Implementation of integrity rules, Question 1 Describe the following- ...

Question 1 Describe the following- Clustering Indexing Question 2 Explain the following with suitable real time examples- Implementation of Integrity rules

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

Functional dependency, Functional Dependency Consider a relation R that...

Functional Dependency Consider a relation R that has 2 attributes A and B. The attribute B of the relation is functionally dependent on the attribute A if and only if for every

What are the components of storage manager, What are the components of stor...

What are the components of storage manager? The storage manager components include a) Authorization and integrity manager b) Transaction manager c) Buffer manager d

Oracle RDBMS, compare the features of oracle RDBMS with MySQL and Microsoft...

compare the features of oracle RDBMS with MySQL and Microsoft SQL server

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