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

Dataware house, ) Define a job scheduling strategy that will meet business ...

) 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 picto

Create the database in oracle using ddl, The Assessment page has a link to ...

The Assessment page has a link to download a conceptual model, and a list of data. You are to map this conceptual model, and create the database in Oracle using your own DDL.  T

Insert - referential integrity, The insertion of a tuple in the aim of refe...

The insertion of a tuple in the aim of reference does not cause any destruction. Though, insertion of a tuple in the relation in which, we has the foreign key, for instance, in ASS

Explain the steps for reduction of e-r model, Explain the steps for reducti...

Explain the steps for reduction of E-R model into relational model. Ans:(a) Entity set in E-R model will be considered as table name in relational Model. (b) Attributes of e

Deadlock and its prevention, Deadlock And Its Prevention: As seen earlier,...

Deadlock And Its Prevention: As seen earlier, though two phase locking protocol handles the trouble of serialisability, but it causes some troubles also. For instance, consider th

Explain i command in qbe, Explain I command in QBE ? I : It is the co...

Explain I command in QBE ? I : It is the command in QBE that is used to insert tuple (s) into the database

Objectives-transactions and concurrency management, Objectives After Re...

Objectives After Reading this part, you should be able to: Explain the term CONCURRENCY; Describe the term transaction and concurrent transactions; Talk about co

Distributed database management system, Question (a) Differentiate betw...

Question (a) Differentiate between the following terms: (i) Distributed Database v/s Distributed Database management System (ii) Homogeneous Distributed Database v/s Hete

What is a value, What is a value? A data value is used for identity. Th...

What is a value? A data value is used for identity. This form of identity is used in relational systems.eg: The primary key value of a tuple recognize the tuple.

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