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

Differentiate between logical database design and physical, Differentiate b...

Differentiate between logical database design and physical database design. Show how this separation leads to data independence? Basis Logical Databas

Data base model, why are older data base model are being replaced by new da...

why are older data base model are being replaced by new data model

Why were functional methods fashionable in early days, Why were functional ...

Why were functional methods fashionable in early days? These are inspired directly by computer architecture and thus popular among computer scientist in early days. The divisio

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.

DISTIBUTED DATABASE, Define physical image of a global relation at a site

Define physical image of a global relation at a site

Whta is the advantage of the database management approach, Whta is the adva...

Whta is the advantage of the database management approach? The advantage of the database management approach is data is integrated and can be accessed by multiple programs.

Update city of first bank corporation to new delhi, Change the city of Firs...

Change the city of First Bank Corporation to ‘New Delhi' UPDATE COMPANY SET CITY = ‘New Delhi' WHERE COMPANY_NAME = ‘First Bank Corporation';

List the sql domain types, List the SQL domain Types? SQL supports the ...

List the SQL domain Types? SQL supports the following domain types. 1) Char(n) 2) varchar(n) 3) int 4) numeric(p,d) 5) float(n) 6) date.

Objectives-file organisation in dbms, Objectives  After reading this un...

Objectives  After reading this unit you should be able to: Explain storage of databases on hard disks; Discuss the execution of various file Organisation techniques;

How we can implement relationships when designing tables, You want to imple...

You want to implement following relationships when designing tables. How would you do it? a.) One-to-one b.) One-to-many c.) Many-to-many a.) One-to-One relationship -

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