Tag: unary relationship in dbms

Relationship Sets | DBMS

Database Management System

Relationship in DBMS-

 

Before you go through this article, make sure that you have gone through the previous article on Introduction to ER Diagrams.

 

A relationship is defined as an association among several entities.

 

Example-

 

‘Enrolled in’ is a relationship that exists between entities Student and Course.

 

 

Also read- Entity Sets in DBMS

 

Relationship Set-

 

A relationship set is a set of relationships of same type.

 

Example-

 

Set representation of above ER diagram is-

 

 

Degree of a Relationship Set-

 

The number of entity sets that participate in a relationship set is termed as the degree of that relationship set. Thus,

 

Degree of a relationship set = Number of entity sets participating in a relationship set

 

Types of Relationship Sets-

 

On the basis of degree of a relationship set, a relationship set can be classified into the following types-

 

 

  1. Unary relationship set
  2. Binary relationship set
  3. Ternary relationship set
  4. N-ary relationship set

 

1. Unary Relationship Set-

 

Unary relationship set is a relationship set where only one entity set participates in a relationship set.

 

Example-

One person is married to only one person

 

 

2. Binary Relationship Set-

 

Binary relationship set is a relationship set where two entity sets participate in a relationship set.

 

Example-

Student is enrolled in a Course

 

 

3. Ternary Relationship Set-

 

Ternary relationship set is a relationship set where three entity sets participate in a relationship set.

 

Example-

 

 

4. N-ary Relationship Set-

 

N-ary relationship set is a relationship set where ‘n’ entity sets participate in a relationship set.

 

Next Article- Cardinality in ER Diagram

 

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