Cardinality Ratioa

Cardinality Ratio

The cardinality ratio for a binary relationship specifies the number of relationship instances that an entity can participate in. 

There are three types of cardinality ratios for binary relationships. 

one-to-one   (1: 1) 
one-to-many  (1 : N)
many-to-many.(N : M) 

one-to-one

one-to-many

many-to-many