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

single products ordered, For Colorado customers calculate the number of si...

For Colorado customers calculate the number of single products ordered. If a product is purchased on multiple orders, it should be counted only single time. The result should conta

Logical operators-logical operators, Logical Operators Rules of Preced...

Logical Operators Rules of Precedence: Order evaluated Operator 1 All comparison operators 2

Develop a fragment of a hypothetical system, The objectives of this assignm...

The objectives of this assignment are:  - to develop skills in the design of database driven applications  - to develop skills in applying SQL to implement the relational and

A b-tree of order how much children m has maximum, A B-tree of order how mu...

A B-tree of order how much children m has maximum ? m has maximum m mchildren in a B tree.

Answer, Describe multi key files

Describe multi key files

What is d command work in the respect of qbe, What is D command work in the...

What is D command work in the respect of QBE? D: It is the command inside QBE to delete tuple(s) from the relation.

Data dictionary, how to prepare a data dictionary for online examination sy...

how to prepare a data dictionary for online examination system for certified courses?

Process of implementing system design in dynamic models, Process of impleme...

Process of implementing system design in dynamic models There are three essential approaches to implementing system design in dynamic models. These approaches are as below:

Basics of relational models, In the first unit of this block, you have been...

In the first unit of this block, you have been given with the details of the Database Management System, its structure, advantages etc. This unit is an attempt to give you informat

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