Cardinality Ratio in DBMS

Cardinality Ratio in DBMS

In this article, we will learn about the Cardinality Ratio in DBMS.
DBMS
  • Cardinality tells how many times the entity of an entity set participates in a relationship
  • There are 4 types of cardinalities
    • One to one
    • One to many
    • Many to one
    • Many to many
Cardinality Ratio in DBMS

1. One to one cardinality

  • When a single instance of an entity is associated with a single instance of another entity, then it is called a one to one cardinality
  • Here each entity of the entity set participates only once in the relationship.
One to One Relationship Cardinality in DBMS

2. One-to-Many  cardinality

  • When is a single instance of an entity is associated with more than one instance of another entity then this type of relationship is called one to many relationships
  • Here entities in one entity set can take participation in any number of times in relationships set and entities in another entity set can take participation only once in a relationship set.
One to Many Relationship Cardinality in DBMS

3. Many-to-one cardinality

When entities in one entity set can participate only once in a relationship set and entities in another entity can participate more than once in the relationship set,  then such type of cardinality is called many-to-one

Many to One Relationship Cardinality in DBMS

4. Many-to-many cardinality

  • Here  more than one instance of an entity is associated with more than one instance of another entity then it is called many to many relationships
  • In this cardinality, entities in all entity sets can take participate any number of times in the relationship cardinality is many to many.
Many to Many Cardinality in DBMS
Learn more about DBMS here on this page.