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

Difference between internal tables and extra datasets, What is the differen...

What is the difference between internal tables and extract datasets? The lines of an internal table always have the similar structure. By using extract datasets, you can ha

What are the functions of an accumulator, What are the functions of an accu...

What are the functions of an accumulator? The accumulator is the register associated with the ALU operations and sometimes I/O operations. It is an integral part of ALU. It hol

Data mining, 1.Why we need data mining? Give an example to illustrate your ...

1.Why we need data mining? Give an example to illustrate your answer. 2. Why data mining is considered as "misleading name"? 3. Distinguish the difference between database an

Implementing a data mining algorithm, i need to implememnt a treee based mi...

i need to implememnt a treee based mining algorithm. do you have an expert that can do that?

Explain dynamic two-phase locking, Explain Dynamic Two-Phase Locking H...

Explain Dynamic Two-Phase Locking Here a transaction locks a data item instantly earlier than any operation is applied on the data item.  After finishing all the operations on

Determine the advantage of object-orientation, Determine the advantage of o...

Determine the advantage of object-orientation Finally, object-orientation has advantage of continuity throughout analysis, persistent representation and design implementation.

Draw enhanced er-diagram for hierarchy of a student database, Draw an EER d...

Draw an EER diagram that captures the "is-a" hierarchy of students in another simple database. The database captures both the "basic" information (say, student ID and student name)

Idea for fyp, want a idea for final year project

want a idea for final year project

What are composite objects, What are composite objects? Objects that ha...

What are composite objects? Objects that have other objects are known as complex objects or composite objects.

What is data storage, What is Data Storage? The storage structures and ...

What is Data Storage? The storage structures and access methods used by database system are specified by a set of explanation in a special type of DDL called data storage-defin

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