Referential integrity, Database Management System

Assignment Help:

It can be easily defined as:

The database must not have any unmatched foreign key values.

The term "unmatched foreign key value" means a foreign key value for which there does not exist a matching value of the relevant candidate key in the relevant target (referenced) relation. For instance, any value existing in the EMPID attribute in ASSIGNMENT relation must be in the EMPLOYEE relation. That is, the only EMPIDs that can be in the EMPLOYEE relation are 101, 102 and 103 for the instance / present state of the database given in Figure. If we want to insert a tuple with EMPID value 104 in the ASSIGNMENT relation, it will cause violation of referential integrity constraint. Logically it is very obvious after all the employee 104 does not be, so how can s/he be assigned any work.


Related Discussions:- Referential integrity

What is the use of group by clause, What is the use of group by clause? ...

What is the use of group by clause? Group by clause is used to be relevant aggregate functions to a set of tuples. The attributes given in the group by clause are used to shape

Explain concurrency control, Explain concurrency control? Concurrency ...

Explain concurrency control? Concurrency control Oracles multiversion concurrency control varies from the concurrency mechanism used by some other data base vendors. Read

The structured query language, The Structured Query Language INTRODUCT...

The Structured Query Language INTRODUCTION Database is an organised set of information about an entity having controlled redundancy and serves numerous applications. DBMS

What is the use of sub queries, What is the use of sub queries? A sub q...

What is the use of sub queries? A sub query is a select-from-where expression that is nested with in another query. A common use of sub queries is to do tests for set membershi

Determine the objectives of object oriented design, Determine the Objective...

Determine the Objectives of object oriented design provide an overview of object oriented design; partitioning system to subsystems; describe how a software desig

Designing the fields in the data base, Designing the fields in the data bas...

Designing the fields in the data base The following are the considerations one has to remain in mind while designing the fields in the data base. Coding, compression, en

Entity integrity constraint - relational constraints, It defines that no pr...

It defines that no primary key value can be null. This is as the primary key is used to recognize individual tuple in the relation. So we will not be able to recognize the records

Transaction, .#question. Discuss the problem which may arise during concurr...

.#question. Discuss the problem which may arise during concurrency control and recovery in distributed database which are not encountered in controlized database environment.

In e-r diagram how derived attribute are represented, In E-R Diagram how de...

In E-R Diagram how derived attribute are represented ? In E-R Diagram By Dashed ellipse derived attribute are represented.

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