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

Explain two phase locking protocol, Explain Two phase locking protocol ...

Explain Two phase locking protocol A transaction is consider as to follow the two-phase locking protocol if all locking operations precede the first unlock operation in the tra

Database schema, #Use the following database schema: 1) Patient—PatientID, ...

#Use the following database schema: 1) Patient—PatientID, Name, DOB 2) Doctor—DoctorID, Name, MedLicenseNumber, Phone 3) Medication—MedicationID, BrandName, GenericName 4) Prescrip

What is business intelligence, Question A What is operational intelligence...

Question A What is operational intelligence? Question B What is Business Intelligence? Explain the components of BI architecture Question C Differentiate between databas

What is a checkpoint, What is a checkpoint? List the operations to be perfo...

What is a checkpoint? List the operations to be performed by the system when a checkpoint is to be taken. What does the recovery system do if there is a crash? There is large n

Data analyzing and desing, Critically explained the benefits and limit...

Critically explained the benefits and limitations of different database technologies with proper examples

Functional dependency in entities, FDs in Entities : Student entity : ...

FDs in Entities : Student entity :                                                Enrolment number →  Student name, Address Course Entity :

Multi-key file organisation, Multi-Key File Organisation In this part, ...

Multi-Key File Organisation In this part, we will introduce two basic file Organisation schemes that permit records to be accessed by more than one key field, therefore, allowi

Entity relationship model, Let us first look into some of the important fea...

Let us first look into some of the important features of ER model. Entity relationship model is a high-level conceptual data model. It permits us to define the data invo

Explain b-tree, What is B-Tree? A B-tree eliminates the redundant stora...

What is B-Tree? A B-tree eliminates the redundant storage of search-key values .It permits search key values to appear only once.

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