Entity integrity constraint - relational constraints, Database Management System

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.

Posted Date: 3/6/2013 5:31:24 AM | Location : United States







Related Discussions:- Entity integrity constraint - relational constraints, Assignment Help, Ask Question on Entity integrity constraint - relational constraints, Get Answer, Expert's Help, Entity integrity constraint - relational constraints Discussions

Write discussion on Entity integrity constraint - relational constraints
Your posts are moderated
Related Questions
Record based Logical Models: Use records as the key data representation components Examples: Relational Model: It shows data as well as relationship between data in the form

Why 'AS' clause is used in SQL ? 'As' clause is used for Rename operation. ‘AS' clause is used in SQL for rename operation. (e.g., SELECT ENO AS EMPLOYEE_NO FROM EMP)

client server architeutre

Example - ALTER TABLE emp MODIFY (empno NUMBER (7));

Problem 1. Write an assembly program to find the smallest among two numbers Writing an assembly program to find the smallest among two numbers 2. Explain the intern


Primary Index In primary index, there is a one-to-one relationship among the entries in the index table and the records in the major table. Primary index can be of two types:

What is an ER diagram? Why is it used in Database management system (DBMS)?

State the Steps of Object Design Object design is a very iterative process in which various classes, relationships among objects are added when you move from one level to

The Structured Query Language INTRODUCTION Database is an organised set of information about an entity having controlled redundancy and serves numerous applications. DBMS