• Mapping Cardinality
– One-to-one:
• We draw a directed line from the relationship set advisor to both entity sets
instructor and student. This indicates that an instructor may advise at most
one student, and a student may have at most one advisor.
– One-to-many:
• We draw a directed line from the relationship set advisor to the entity set
instructor and an undirected line to the entity set student. This indicates that
an instructor may advise many students, but a student may have at most one
advisor.
– Many-to-one:
• We draw an undirected line from the relationship set advisor to the entity set
instructor and a directed line to the entity set student. This indicates that an
instructor may advise at most one student, but a student may have many
advisors.
– Many-to-many:
• We draw an un directed line from the relationship set advisor to both entity
sets instructor and student. This indicates that an instructor may advise many
students, and a student may have many advisors.