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

Data warehouse, XYZ is a large chain of home entertainment rental over 100 ...

XYZ is a large chain of home entertainment rental over 100 stores distributed over all states in Australia. XYZ lends entertainment products such as movies, TV shows and games on v

Explain what is relation, Explain What is Relation? A database relatio...

Explain What is Relation? A database relation is a predefined row or column format for storing information in a relational database. Relations are equal to tables.

Determine the types of methods for retrieving rows in python, Describe the ...

Describe the two types of methods for retrieving rows in Python? Fetchone()- Returns the next row as a sequence Fetch all()- Returns the entire result set like a strin

Explain what is rdbms, Explain what is RDBMS ? RDBMS - RDBMS is a datab...

Explain what is RDBMS ? RDBMS - RDBMS is a database management system (DBMS) which stores data within the form of relations. Relational databases are powerful since they need f

Benefits and drawbacks of sequential file organisation, Benefits of Sequent...

Benefits of Sequential File Organisation It is quick and efficient when dealing with huge volumes of data that require being processed periodically (batch system). Dra

Object-based models - data models, Object-based Models: Use objects as key ...

Object-based Models: Use objects as key data representation components . Examples:-   Entity-Relationship Model: It is a collection of real world objects known as entitie

What is called a query -execution engine, What is called a query -execution...

What is called a query -execution engine? The query implementation engine takes a query evaluation plan, implements that plan, and returns the answers to the query.

Explain outer join, Explain outer join? Outer Join - If there are any...

Explain outer join? Outer Join - If there are any values in one table which do not have corresponding value(s) in the other, in an equi-join which will not be chosen. Such ro

Physical database design issues, Physical Database Design Issues The da...

Physical Database Design Issues The database design includes the process of logical design with the use of E-R diagram, normalisation, etc., followed by the physical design.

Clinic, Need a sample of a clinic database relationships

Need a sample of a clinic database relationships

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