1. Entity – Relationship Model

2. Database Design Requirement Analysis Conceptual Design Logical Design
Schema Refinement
Physical Design
Security Design

3. ER Model
Data can be described as
Entities
Relationships
attributes

4. Types of attributes Single attribute Composite attribute
Single – valued attribute
Multi – valued attribute
Stored attribute
Derived attribute
Complex attribute

6. Complex Attribute
Example - AddressPhone {AddressPhone( {Phone(AreaCode,PhoneNumber)},Address (StreetAddress(Number,Street,ApartmentNumber),City,State,Zip) ) }

7. Entity Set
Collection of all entities of the same type.
customer

8. Relationship Set

9. Notations in ER Model

10. E-R Diagram Example

11. E-R Diagram Example

12. E-R Diagram Example

13. Degree of a Relationship
Degree- number of participating entity types.
Degree = 1 – unary
Degree = 2 – binary
Degree = 3 – ternary
Degree = n – n-ary

14. Example - Unary

15. Example - Binary

16. Example - Ternary

17. Rolename
Identifies the exact role in which the entity participates in the relationship.

18. Recursive Relationship

19. Mapping Cardinalities
One to one
One to many

20. Mapping Cardinalities
Many to one
Many to many

23. ADDITIONAL FEATURES OF THE ER MODEL
Key Constraints

24. Participation Constraints
Total
Partial

25. Weak Entities

26. Class Hierarchies
Specialization
Generalization

30. Aggregation

32. Case Study – Internet Shop
Requirement Analysis
I would like my customers to be able to browse my catalog of books and place orders over the Internet. Currently, I take orders over the phone.
I have mostly corporate customers who call me and give me the ISBN number of a book and a quantity; they often pay by credit card.

33. Case Study – Internet Shop
I then prepare a shipment that contains the books they ordered. If I don't have enough copies in stock, I order additional copies and delay the shipment until the new copies arrive;
I want to ship a customer's entire order together.
My catalog includes all the books I sell.

34. Case Study – Internet Shop
For each book, the catalog contains its ISBN number, title, author, purcha.se price, sales price, and the year the book was published. Most of my customers are regulars, and I have records with their names and addresses.

35. Case Study – Internet Shop
Conceptual Design

36. ER Model for the company database