Key constraint - relational constraints, Database Management System

Assignment Help:

This constraint shows that the key attribute value in each tuple must be unique, i.e., no two tuples have the similar value for the key attribute. This is because the value of the primary key is used to recognize the tuples in the relation.

 

Example: If A is the key attribute in the following relation R than A1, A2 and A3 must be unique.

 

A

 

B

 

A1

 

B1

 

A3

 

B2

 

A2

 

B2

 

Example: In relation PERSON, PERSON_ID is primary key so PERSON_ID cannot be given as the similar for two persons.

Integrity Constraint

There are two kinds of integrity constraints:

  • Entity Integrity Constraint
  • Referential Integrity Constraint

Related Discussions:- Key constraint - relational constraints

Write short note on events, Write short note on Events Events consist ...

Write short note on Events Events consist of inputs, interrupts, decisions and actions performed by any external device or users. Every event always has a sender and receiver.

Write a program within embedded sql to associative relation, Write a progra...

Write a program within embedded SQL to associative the total trip expenses of the salesman named ‘John' for the relations. EXEC SQL BEGIN DECLARE SECTION; long total_expenses;

Cataloguing, differences between a classified catalog and a dictionary cata...

differences between a classified catalog and a dictionary catalog

E-commerce and business intelligence systems., Your friend owns and operate...

Your friend owns and operates a wholesale shoe business with annual revenues of $5 million dollars. His wholesale business specializes in supplying and supporting retailers with sh

Explain the isa relationship, Explain the ISA relationship Answer: IS...

Explain the ISA relationship Answer: ISA relationship - ISA notation is employed in generalization/ specialization to depict relationship among lower and higer level entity s

Research in Concurency Control Protocols, Performance of Various Concurrenc...

Performance of Various Concurrency Control Mechanisms

How the one-to-one associations have to be implemented, Discuss how the one...

Discuss how the one-to-one associations have to be implemented. Some of properties of associations can be implemented directly by providing suitable declarations of the data me

Describe query evaluation engine, Describe Query evaluation engine? Que...

Describe Query evaluation engine? Query Evaluation engine: Vehicle executes low-level instructions obtained through the DML compiler. The Storage Manager Components gives in

Describe the grant function and explain security, Describe the GRANT functi...

Describe the GRANT function and explain, how it associates to security. What kind of privileges may be granted? How are they revoked? Ans: Since more than one user can aacce

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