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

Max. no. of structures in a table or structure, What is the max. no. Of str...

What is the max. no. Of structures that can be included in a table or structure. Nine.

What is a project operation, What is a PROJECT operation? The project o...

What is a PROJECT operation? The project operation is a unary operation that returns its argument relation with particular attributes left out. Projection is shown by pie (π).

Data warehouse, 1) Define a job scheduling strategy that will meet business...

1) 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 pict

Describe models which define the operations on classes, Describe briefly mo...

Describe briefly models which define the operations on classes. The three models which are used to define operations on classes are as: Object Model = data dictionary + Obje

Domains, A domain is a set of permissible values that can be given to an at...

A domain is a set of permissible values that can be given to an attribute. So each attribute in a table has a definite domain. Values to these attributes cannot be assigned outside

Describe sequential file organization, Describe sequential file organizatio...

Describe sequential file organization.  Explain the rules for (i)  Inserting a new record. (ii)  Deleting an existing record.          Ans:A sequential f

Er-diagram, courier company er-diagram

courier company er-diagram

What is online transaction processing, What is OLTP (Online Transaction Pro...

What is OLTP (Online Transaction Processing)? In OLTP - online transaction processing systems relational database design use the discipline of data modeling and generally follo

Define null values, Define null values. In some cases a certain entity ...

Define null values. In some cases a certain entity may not have an applicable value for an attribute or if we do not know the value of an attribute for a certain entity. In the

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