The sample diagram (figure 2-1) on page 98 has cardinalities in the key and figure 2-2 on page 100 talks about relationship cardinality. To help us understand the process of creating E-R diagrams and at the same time make it easier, relationship cardinality as it is described in the book will not be used at all in this unit.
To represent one-one, one-many or many-many relationships, we will just show the connectivity as follows:
We do not show mandatory or optional cardinality.