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

Determine the subsystem design issue, Determine the Other System Design Iss...

Determine the Other System Design Issue How to realise subsystems; through hardware or software? How is object model mapped on chosen hardware software? Mapping

Process of implementing system design in dynamic models, Process of impleme...

Process of implementing system design in dynamic models There are three essential approaches to implementing system design in dynamic models. These approaches are as below:

Create database for car application, The Database MySQL scripts cars_f...

The Database MySQL scripts cars_for_sale.sql and car_details.sql containing the data to use for this task have been supplied. To complete this task, you need to first create

Construct substantial data model, PART MARKING:  We will only mark TWO of t...

PART MARKING:  We will only mark TWO of the four questions below but you must submit answers to all four. We will choose the questions we mark randomly and we will supply you with

Structure of the ldb, Though all the ABAP/4 Dictionary Structures that exis...

Though all the ABAP/4 Dictionary Structures that exists in the structure of the LDB, being described in Database Program, we are explaining the Dictionary Structures in the Report.

Normalization, Consider a bank that has a collection of sites, each running...

Consider a bank that has a collection of sites, each running a database system. Suppose the only way the databases interact is by electronic transfer of money between one another,

Decomposition, properties of derirable decomposition

properties of derirable decomposition

What are the two statements regarding transaction, What are the two stateme...

What are the two statements regarding transaction? The two statements regarding transaction of the form are:- A)     Begin transaction B)      End transaction

MIS, We face problem of stock Opening balance and closing balance in Minus...

We face problem of stock Opening balance and closing balance in Minus

Write expressions in relational algebra, Given the subsequent relations: ...

Given the subsequent relations:    vehicle (reg_no, make, colour)    Person (eno, name, address)    Owner (eno, reg_no)   Write expressions

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