Describes the several relationship constraints, Database Management System

Describes the several relationship constraints through giving suitable example?

Constraints on relationships: There are two kinds of constraints on relationships.

1) Mapping cardinalities or cardinality ratios express the number of entities to that another entity can be associated through a relationship set. For a binary relationship set among entities A and B. The mapping cardinality may be any one of the subsequent:

a) One to One: An entity in A is related along with at most one entity in B and an entity in B is related with at most one entity in A.
b) One to Many: An entity in A can be related with any number in B but an entity in B is associated with at most one in A.
c) Many to one: An entity in A is related with at most one in B but an entity in B is associated with any number in A.
d) Many to Many: An entity in A and B can be associated along with any number of entities in the other entity set.

2) Participation constraints: The participation of an entity set E in a relationship set R is said to be total if every entity in E participates within at least one relationship in R. If only a few entities in E participation of entity set E in relationship R is said to be partial.

Posted Date: 5/13/2013 2:21:12 AM | Location : United States







Related Discussions:- Describes the several relationship constraints, Assignment Help, Ask Question on Describes the several relationship constraints, Get Answer, Expert's Help, Describes the several relationship constraints Discussions

Write discussion on Describes the several relationship constraints
Your posts are moderated
Related Questions
Explain I command in QBE ? I : It is the command in QBE that is used to insert tuple (s) into the database

we need example of 2phase locking


What is ODBC ? ODBC - Open DataBase Connectivity which is also denoted by ODBC enable the integration of SQL along with a common-purpose programming language. ODBC expose data

Explain the term - Adjustment of inheritance The inheritance can be enlarged as object design progresses by changing class structure. The designer should do: i) Adjust or r

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

The following variant of the primary copy asynchronous-update replication protocol has been proposed for totally replicated systems. (a)  A transaction executing at site A updat

What is the use of keyword ISA? The use of keyword ISA is to show that a class is a specialization of another class.

What is object identity? An object retains its identity even if some or all the values of variables or explanations of methods change overtime.

What is schema