Entity integrity, Database Management System

Assignment Help:

Before defines the second type of integrity constraint, viz., Entity Integrity, we should be well-known with the concept of NULL.

Mostly, NULL is intended as a basis for dealing with the trouble of missing information. This type of situation is frequently encountered in the actual world. For instance, historical records sometimes have entries such as "Date of birth unknown", or police records may contain the entry "Present whereabouts unknown." Therefore it is necessary to have some way of dealing with such concepts in database systems.

Therefore Codd proposed an approach to this issue that creates use of special markers known as NULL to show such missing information.

A given attribute in the relation may or may not be allowed to include NULL. However, can the Primary key or any of its components (in case of the primary key is a composite key) contain a NULL? To answer this Query an Entity Integrity Rule states: No component of the primary key of a relation is permitted to accept NULL. In different words, the definition of each attribute involved in the primary key of any basic relation have to explicitly or implicitly contain the specifications of NULL NOT ALLOWED.


Related Discussions:- Entity integrity

Normalization, Process of normalization is the integral part of designing a...

Process of normalization is the integral part of designing a database. Justify this statement with suitable database design

What is the initial step for object-oriented designing, What is the initial...

What is the initial step for object-oriented designing The initial step for object-oriented designing is object modeling. Before we go into deep about object modeling first of

By which techniquestransaction processing is associated, By which technique...

By which techniquesTransaction processing is associated? Transaction processing is associated by producing detail, summary, or exception reports and recording a business activi

Which operator is cartesian product in relational algebra, Which operator i...

Which operator is Cartesian product in relational algebra? Cartesian product in relational algebra is a binary operator. (It requires two operands. e.g., P X Q)

Linked list, what is difference between circular inked lust and grunded lin...

what is difference between circular inked lust and grunded linked list

Hangman, a method named WonGame that checks each letter in the word is matc...

a method named WonGame that checks each letter in the word is matched by its label

Create the table, Question: Using the data model express the following ...

Question: Using the data model express the following queries in SQL. (a) Create the Table named "Cinema" and make the cinema_code to be the primary key of the relation and

BI, (a) Why did SAP introduce the extended star schema?

(a) Why did SAP introduce the extended star schema?

Student database, tell me the functionality,advantages and disadvantages of...

tell me the functionality,advantages and disadvantages of student 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