Key constraint - relational constraints, Database Management System

Assignment Help:

This constraint shows that the key attribute value in each tuple must be unique, i.e., no two tuples have the similar value for the key attribute. This is because the value of the primary key is used to recognize the tuples in the relation.

 

Example: If A is the key attribute in the following relation R than A1, A2 and A3 must be unique.

 

A

 

B

 

A1

 

B1

 

A3

 

B2

 

A2

 

B2

 

Example: In relation PERSON, PERSON_ID is primary key so PERSON_ID cannot be given as the similar for two persons.

Integrity Constraint

There are two kinds of integrity constraints:

  • Entity Integrity Constraint
  • Referential Integrity Constraint

Related Discussions:- Key constraint - relational constraints

Super keys, A super key is an attribute or set of attributes used to recogn...

A super key is an attribute or set of attributes used to recognize the records uniquely in a relation. For instance, in the Relation PERSON defines earlier PERSON_ID is a super

Describe graphical user interface, Describe Graphical User Interface? ...

Describe Graphical User Interface? Graphical User Interfaces (GUIs) - A GUI typically displays a schema to the user in diagrammatic form. The user can then specify a query th

Data manipulation language, Data Manipulation Language Data manipulatio...

Data Manipulation Language Data manipulation language (DML) describes a set of commands that are used to query and change data within existing schema objects. In this case comm

Explain the static or conservative two phase locking, Explain the Static or...

Explain the Static or conservative Two Phase Locking: Static (or conservative) Two Phase Locking: In this type of scheme, all the data items are locked earlier than any opera

List the requirements needed to design a trigger, List the requirements nee...

List the requirements needed to design a trigger. The requirements are:- Specifying when a trigger is to be implemented. State the actions to be taken when the trigger im

Insulation between conceptual and physical structures, Insulation between c...

Insulation between conceptual and physical structures It can be defined as: 1. The Database Administrator should be capable to vary the storage structures without affectin

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

Describe interfaces for the dba, Describe Interfaces for the DBA? Inte...

Describe Interfaces for the DBA? Interfaces for the DBA - Most database systems holds privileged commands which could be used only through the DBA's staff. These involves com

What is conceptual schema, What is conceptual schema? The schemas at th...

What is conceptual schema? The schemas at the view level are known as subschema that describe dissimilar views of the database.

Checkpoint, what is check point in database management system

what is check point in database management system

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