Relationship and Cardinality

Relationship and Cardinality are essential part of database design.

Table of Contents

Relationships describes

the number of instances of one entity that can be associated with the number of instances of another entity within a relationship.

Cardinality constraints ensure data integrity by defining the permissible number of relationships between entities.
Cardinality helps in accurately representing the relationships between entities. It clarifies whether a relationship is one-to-one, one-to-many, many-to-one, or many-to-many, providing a clear understanding of how instances in one entity are associated with instances in another.
Cardinality constraints contribute to normalization by guiding the designer in structuring relationships in a way that avoids unnecessary duplication of data.
Knowing the cardinality of relationships allows database management systems to optimize queries more effectively.
When designing databases, cardinality provides a clear communication mechanism for developers, database administrators, and other stakeholders involved in the project. It facilitates a shared understanding of how different entities are related and how data flows through the system.
Cardinality constraints assist in preventing update, insertion, and deletion anomalies by defining rules for how data can be modified within related entities. This contributes to the overall consistency and reliability of the database.