Entity Relationship Diagram:
An Entity relationship diagram describe the how entities such as people, jackpot concert relate to each other within a system. There ERD are composed of entities, relationships and attributes. Now we will see how entities and attributes are relationshiped with help of ERD components.
Rectangle:Entities are represented by rectangle
Double Rectangle: A weak entity is represented in the double rectangle and it is implemented by foreign key relationship with another entity.
Diamond Shape: Relationship / action are represented by diamond.
Ellipse /Oval: Attributes are represented by ellipses /oval
Double Ellipse: An attribute can have more than one field / value like phone number so it is represented in double ellipse.
Dashed Ellipse Or Derived Attribute:
Attribute which is based on another attribute are called derived attribute and they are represented by dashed ellipse.
Lines: They are ways of showing relationship and cardinality.
Binary relationship and cardinality:
One to One :
One to Many:
Many to One:
Many to Many:
Representation of Participation Constraints
