Avon Products ER Diagram
What are Entity Relationship Diagram?
Entity
An entity is an object or concept about which you want to store information.
Key attribute
A key attribute is the unique, distinguishing characteristic of the entity. For example, an employee's social security number might be the employee's key attribute.
Relationships
Relationships illustrate how two entities share information in the database structure.
Cardinality
Cardinality specifies how many instances of an entity relate to one instance of another entity.
Ordinality is also closely linked to cardinality. While cardinality specifies the occurences of a relationship, ordinality describes the relationship as either mandatory or optional. In other words, cardinality specifies the maximum number of relationships and ordinality specifies the absolute minimum number of relationships.