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

Explain the reason for keeping legacy system, In order to keep pace with co...

In order to keep pace with competitors, Space Ltd has decided to implement an ERP system in order to replace its old legacy and manual systems. Management does not have much knowle

What is outer join, What is Outer join?  They can be employed while we ...

What is Outer join?  They can be employed while we want to keep all the tuples in R, or all those in S or all those in both relations in the result of the JOIN in spite of of w

Describe the two alternatives for specifying structural, Describe the two a...

Describe the two alternatives for specifying structural constraints on relationship kinds? Relationship kinds have certain constraints in which limit the possible combination o

Explain discretionary access control, Problem: (a) Given the following ...

Problem: (a) Given the following relation: Stats(Name,Sex,Children, Occupation, Salary, Tax, Audits) Write SQL code to define the following security constraints: (i) User

Design and build a data mart, You are required to design and build a data m...

You are required to design and build a data mart/data warehouse using Oracle. A national bank allocates funding every year for its local branches to provide temporary staff cove

Improve efficiency of database, Smart Alex Catering Sevice (SACS) is a comp...

Smart Alex Catering Sevice (SACS) is a company offering top class catering staff  for prestigious events.  The company employs approximately 200 hourly paid contact staff - chefs,

Accounting and external reporting, List the internal controls that should b...

List the internal controls that should be in effect solely because a EDP system is employed, classifing them as (1) Those controls pertaining to input of information and (2) All ot

Explain recovery process after system failure, Explain recovery process aft...

Explain recovery process after system failure using checkpoint. Ans: Checkpoint scheme or method is an extra component of the log based recovery system. This scheme is used to

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