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

Objectives of database manangement system, OBJECTIVES After going thro...

OBJECTIVES After going through this unit you should be capable to: Explain the File Based system and its limitations; Explain the structure of DBMS; Explain the

Construct a conceptual data model, Competition entrants can be either Indiv...

Competition entrants can be either Individuals, or Teams. A Team is usually sponsored by a business, and, in that case, the team members would all wear T-shirts with the sponsoring

Assigning responsibility for operation, Assigning Responsibility for Operat...

Assigning Responsibility for Operation Many operations might have obvious target objects, but some of these operations could be used at numerous places in an algorithm, by one

Lock, intent locking

intent locking

Physical dbms architecture, PHYSICAL DBMS ARCHITECTURE  The physical ...

PHYSICAL DBMS ARCHITECTURE  The physical architecture defines the software components used to process and enter data, and how these software components are related and interc

Query evolution, what is query processing ,query optimization and performan...

what is query processing ,query optimization and performance turring?

What is structured query langauge, What is Structured Query Langauge (SQL)?...

What is Structured Query Langauge (SQL)? SQL is a powerful set-oriented language which was formed by IBM research for the databases that adhere to the relational model. It havi

Differentiate between horizontal and mixed partitioning, Question: In r...

Question: In relation to distributed database answer the following questions: (i) Give a brief definition of distributed database. Support your answer with an appropriate di

What is the difference between serial and sequential files, What is the dif...

What is the difference between serial and sequential files? How searching is applied on both?    Ans: A serial file is one where the records have been stored in the order where

Update anomaly-data redundancy, Update Anomaly : This anomaly is occurred d...

Update Anomaly : This anomaly is occurred due to data redundancy. Redundant information makes updates more complex since, for example, varying the name of the instructor of MCS-014

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