Key constraint - relational constraints, Database Management System

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
Posted Date: 3/6/2013 5:30:34 AM | Location : United States







Related Discussions:- Key constraint - relational constraints, Assignment Help, Ask Question on Key constraint - relational constraints, Get Answer, Expert's Help, Key constraint - relational constraints Discussions

Write discussion on Key constraint - relational constraints
Your posts are moderated
Related Questions
need a DBMS system on any data for assignment.

In E-R diagram how generalization is represented? in E-R diagram generalization is represented by Triangle shape.

Automated system for appointment with sms and call confirmation with service providers and user has to be initiate automatically. After selecting time and date to use service, s

Consider an information system designed for an online company which provides IT products and services These include desktops, laptops, networking products, IT books, parts, and

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

How do you find the final model after iterative analysis? Why is iterative analysis of any of the problem needed? The final model serves as the base for system architectur

what is difference between circular inked lust and grunded linked list

What are the basic objects of the data dictionary? Tables Domains Data elements Structures Foreign Keys

Every simple attribute of an entity type have a possible set of values that can be attached to it. This is known as the domain of an attribute. An attribute cannot have a value out

Describe the benefits of OOD techniques OOD techniques are very useful for development of large and complex systems. It has been noted that large projects that are developed u