Entity Relationship

One-to-one

One entity object is exactly related to one object of another entity. Ex: Relationship between an Employee and his Personal Details.

One-to-Many

One entity object is related to many objects of another entity. Ex: Relationship between a Department and the Employees working in the department.

Many-to-one

Many objects of an entity are related to one object of another entity. Ex: Relationship between employees and their project i.e. many employees may work for a single project.

Many-to-Many

Many objects of an entity are related to many objects of another entity. Ex: Relationship between employees and courses i.e. many employees may register for either one course or multiple courses.

Relationships.png

 

 

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