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

OLD HOME POLICIES, Write an sql statement to find what is the percentage of...

Write an sql statement to find what is the percentage of home policies which are from the state of Arizona out of all Home policies by Policy Value.

Database administrator, The Database administrator (DBA) uses the data dict...

The Database administrator (DBA) uses the data dictionary in each phase of a database life cycle, beginning from the data gathering phase to the design, execution and maintenance p

Replicating data, Replicating Data One approach that may support effici...

Replicating Data One approach that may support efficient access to dissimilar applications as above may be to give access to every of the applications from dissimilar replicate

Describe the types of inheritance, Describe the types of Inheritance ...

Describe the types of Inheritance 1.  Single inheritance 2.  Multiple inheritance 3.  Hierarchical inheritance 4.  Multilevel inheritance

Database Models, Benefits and Limitations od Data Models?

Benefits and Limitations od Data Models?

Assignment, Birla Institute of Technology & Science, Pilani Work-Integrated...

Birla Institute of Technology & Science, Pilani Work-Integrated Learning Programmes Division Second Semester 2012-2013 EC-1 Assignment 2 (7.5% of the grade) Course No. : SS ZG

Dataware house, ) Define a job scheduling strategy that will meet business ...

) Define a job scheduling strategy that will meet business requirement of reporting availability by 6am CST for the following cubes? Show the job scheduling dependencies in a picto

Describe graphical user interface, Describe Graphical User Interface? ...

Describe Graphical User Interface? Graphical User Interfaces (GUIs) - A GUI typically displays a schema to the user in diagrammatic form. The user can then specify a query th

State the process of inheritance adjustment, Inheritance Adjustment As...

Inheritance Adjustment As in object oriented analysis and design terms inheritance defines a relationship between classes, where as one class shares structure or behaviour def

What is relational model feature, What is relational model feature? A r...

What is relational model feature? A relational model feature is much more data independence than some other database models.

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