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

Prepare heart failure registry database, Prepare Heart Failure Registry dat...

Prepare Heart Failure Registry database How are you today? Please I would like you to design a Heart Failure registry where doctors will log in to enter information about their

Idea for fyp, want a idea for final year project

want a idea for final year project

In tuple relational calculus p1- p2 is equivalent to, In tuple relational ...

In tuple relational calculus P1 → P2 is equivalent to ? A In tuple relational calculus P1→  P2 is equivalent to ¬P1 V P2. (The logical implication expression A  B, meaning

I need helpin assignment, My cut off date is very soon in a Database subjec...

My cut off date is very soon in a Database subject and i dont know how to solve anything in it

Define rule that value of foreign key appear in other table, Determine the ...

Determine the rule that a value of a foreign key should appear as a value of some particular table is called a  Ans: Referential constraint.    The rule that a value of a fo

Mr.dattu, Define a job scheduling strategy that will meet business requirem...

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 pictori

What are axioms, What are axioms? Axioms or rules of inference give a s...

What are axioms? Axioms or rules of inference give a simpler technique for reasoning about

Benefits of using a relational database management system, Question 1: ...

Question 1: a) What is the difference between a non-impact and impact printer? b) Which type of printer is generally used in a supermarket to print your receipt? Describe

Describe the development process of object oriented methods, Describe the d...

Describe the development process of Object oriented methods Object oriented methods have roots which are strongly anchored back in the 60s, functional and structured methods we

Give the reasons for allowing concurrency, Give the reasons for allowing co...

Give the reasons for allowing concurrency? The reasons for allowing concurrency is if the transactions run serially, a short transaction might have to wait for a preceding long

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