1. Entity

2. Attribute

3.Relationsship

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A relationship relates two or more distinct entities with a specific meaning

relationonships of the same type are grouped or typed into a relationship type

Relationship type

• itis a schema descriptionof a relationship
• Identifies the relaionship name and the participationg

Relationship set

• [add something here]

the degree of a relationship type is the number of participating entity types (if degree is 2 its a binary relationship)

Mapping cardinality - 1:1

One entiy in the first entity type is connected to only one entity in the second entity type

1:N

one entity in the first entity type is connected to N entities in the second entity type

N:1

N entities in the first enitty type is connected to 1 entity in the second entity type.

N:N

N entites in the first entity is connectes to N entities in the second entity type

eg: any number of Employees can work for any number of Projects

RElations in ER diagram

in ER diagram,

• diamond shaped box is used to represent the Relationship
• max degree posible is 4
  • 2- binary
  • 3- ternary
  • 4- quaternary