E-R Diagram:  Capture reality.   Do not need to think about using characters or string for ID field instead of # in the table.

• Entity with Attributes
• Relationship
• Constraints:
• Domain Constraint - valid value for each attribute.  Use separate table to describe them.
• Key Constraint - e.g.. Each department has at most one manager.
• Participation Constraint -  e.g. Every department is required to have a manager.
• Type of Relationship Constraints:
• One to One     (at most one to the other side)
• One to Many
• Many to Many
• Binary Relationship vs. Ternary Relationship
• Courses-Students-Teachers
• Restaurant-Food-Supplier
• The case of aggregation
• Insurance Policies - Figures 2.18 & 2.19 on pages 42 & 43
• Weak Entities
• Class Hierarchies

(See figure 2.12 on page 36 - Employee is a Hourly_Emps or a Contract_Emps.)
(Subset concept)
• Overlap constraints  - (eg. Contract_Emps & Senior_Emps)
• Covering constraints - (eg. Hourly_Emps & Contract_Emps vs. Employee)
See restaurant example
• Aggregation vs. Ternary Relationship