Identification of Relationships

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Introduction about relationships

Relationship describe connection between database tables. Relationship is primarily the way to two or more data sets linked. One data set known as the foreign key and the other one is primary key. There may be multiple foreign keys and primary keys linked to each other. 

What are the relationships in ER Diagrams .

          When considering about the relationships in ER diagrams there are three types of relationships that can be exist between two entities.An entity-relationship diagram can be created based on these three types.

One to One relationships (1:1)-

        In relational database design, a One to One relationship exists when zero or one instance of entity A can be associated with zero or one instance of entity B, and zero or one instance of entity B can be associated with zero or one instance of entity A.


 


 

One to Many relationships (1:N)

    In relational database design, a One to Many relationship exists when, for one instance of entity A, there exists zero,one or many instances of entity B, but for one instance of entity B, there exists zero or one instance of entity A.



 

Many to Many relationships (M:N)

    In relational database design, a Many to Many relationship exists when, for one instance of entity. A there exists zero, one or many instances of entity B, add for one instance of entity B, there exists zero , one  or many instances of entity A .


 

 


 When considering our scenario our ER diagram has all above relationships.



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