Entity integrity constraint - relational constraints, Database Management System

Assignment Help:

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 uniquely containing null values for the primary key attributes. This constraint is specified on single individual relation.

 Example: Let R be the Table

A#

B

C

Null

B1

C1

A2

B2

C2

Null

B3

C3

A4

B4

C3

A5

B1

C5

Note:

1) '#' shows the Primary key of a relation.

In the relation R above, the primary key has null values in the tuples t1 & t3. NULL value in primary key is not allowed, therefore, relation instance is an invalid instance.


Related Discussions:- Entity integrity constraint - relational constraints

In how many parts events are classified, In how many parts events are class...

In how many parts events are classified Events are classified as four types in UML 1.  Signals 2.  Calls 3.  Passing of Time 4.  Change in State

List the requirements needed to design a trigger, List the requirements nee...

List the requirements needed to design a trigger. The requirements are:- Specifying when a trigger is to be implemented. State the actions to be taken when the trigger im

To delete a particular column in a relation which command, To delete a part...

To delete a particular column in a relation which command is used ? To delete a particular column in a relation ALTER command is used.

Write a short note on oracle instance, Write a short note on oracle Instanc...

Write a short note on oracle Instance? Oracle Instances: An instance is the (executed) Oracle software and the memory they use. It is the instance which manipulates the data s

Three level architecture of dbms-logical architecture, Three Level Architec...

Three Level Architecture of DBMS or Logical DBMS Architecture The logical architecture defines how data in the database is perceived by users. It is not deals with how the da

Functional Dependencies, What exactly is the concept of Functional Dependen...

What exactly is the concept of Functional Dependencies? And how do we associate this concept with the logic of Super-keys, Candidate Keys, etc? Given Relation R(A,B,C,D,E) with de

What is deadlock, What is deadlock? Neither of the transaction can ever...

What is deadlock? Neither of the transaction can ever proceed with its normal implementation. This situation is known as deadlock.

BCA, Ask qu. Write a XML with database with book details (Book ID, Title, A...

Ask qu. Write a XML with database with book details (Book ID, Title, Author, subject, published year, language, vendor, and price).estion #Minimum 100 words accepted#

Explain the natural join, Explain the Natural join Natural join is a bi...

Explain the Natural join Natural join is a binary operator which is written as (R* S) in which R and S are relations. The effect of the natural join is the set of all combinati

Explain i command in qbe, Explain I command in QBE ? I : It is the co...

Explain I command in QBE ? I : It is the command in QBE that is used to insert tuple (s) into the database

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