1. Relational Database

2. Dr. Edgar F. (Ted) Codd
To fellow pilots and aircrew in the Royal Air Force during World War II and the dons at Oxford: These people were the source of my determination to fight for what I believed was right during the ten or more years in which government, industry, and commerce were strongly opposed to the relational approach to database management.

3. Relational Definitions
Every relation has a unique name.
Every attribute value is atomic.
Every row is unique.
Attributes in tables have unique names.
The order of the columns is irrelevant.
The order of the rows is irrelevant.

4. Relational Definitions
Tuple
Attribute
View

5. Relational Keys and Structures
Primary Key
Candidate Key
Composite Key
Foreign Key
One-to-Many Relationship
Many-to-Many Relationship
Intersection Data

6. Relational Concepts Relational Algebra Relational Calculus
Relational Operations
SELECT
PROJECT
JOIN
Equijoin - Join field appears twice.
Natural Join - Join field appears once.

7. Schema for four relations (Pine Valley Furniture)

8. Instance of a relational schema

9. Integrity Constraints
Domain Constraints
Allowable values for an attribute.
Entity Integrity
No primary key attribute may be null.
Operational Constraints
Business rules.

10. Referential integrity constraints (Pine Valley Furniture)

11. Integrity Constraints
Referential Integrity
For example: Delete Rules
Restrict
Cascade
Set-to-Null

12. Well-Structured Relations
Insertion Anomaly
Deletion Anomaly
Modification Anomaly

13. Transforming E-R Diagrams into Relations
1. Map Regular Entities to Relations (Fig. 6-8).
Composite attributes: Use only their simple, component attributes (Fig. 6-9).
Multi-valued Attribute - Becomes a separate relation with a foreign key taken from the superior entity (Fig. 6-10).

14. Mapping a composite attribute
(a) CUSTOMER entity type with composite attribute

15. (b) CUSTOMER relation with address detail

16. Transforming E-R Diagrams Into Relations
2. Map Weak Entities
Becomes a separate relation with a foreign key taken from the superior entity (Fig. 6-11).

17. Example of mapping a weak entity
(a) Weak entity DEPENDENT

18. (b) Relations resulting from weak entity

19. Transforming E-R Diagrams Into Relations
3. Map Binary Relationships
One-to-Many - Primary key on the one side becomes a foreign key on the many side (Fig. 6-12).
Many-to-Many - Create a new relation with the primary keys of the two entities as its primary key (Fig. 6-13).
One-to-One - Primary key on the mandatory side becomes a foreign key on the optional side (Fig. 6-14).

20. Example of mapping a 1:M relationship
(a) Relationship between customers and orders

21. (b) Mapping the relationship

22. Example of mapping an M:N relationship
(a) Requests relationship (M:N)

23. (b) Three resulting relations

24. Mapping a binary 1:1 relationship

25. (b) Resulting relations

26. Transforming E-R Diagrams Into Relations
4. Map Associative Entities
Identifier Not Assigned
Default primary key for the association relation is the primary keys of the two entities (Fig. 6-15).
Identifier Assigned
It is natural and familiar to end-users.
Default identifier may not be unique.
(Fig. 6-16).

27. Mapping an associative entity with an identifier
(a) Associative entity (SHIPMENT)

28. (b) Three relations

29. Transforming E-R Diagrams Into Relations
5. Map Unary Relationships
One-to-Many - Recursive foreign key in the same relation (Fig. 6-17).
Many-to-Many - Bill-of-materials: Two relations:
One for the entity type.
One for an associative relation in which the primary key has two attributes, both taken from the primary key of the entity. (Fig. 6-18).

30. Transforming E-R Diagrams Into Relations
6. Map Ternary (and n-ary) Relationships
One relation for each entity and one for the associative entity.
(Fig. 6-19).

31. Mapping a ternary relationship
(a) Ternary relationship with associative entity

32. (b) Mapping the ternary relationship

33. Supertype/subtype relationships

34. Mapping Supertype/subtype relationships to relations

35. Data Normalization
Primarily a tool to validate and improve a logical design so that it satisfies certain constraints that avoid unnecessary duplication of data.
The process of decomposing relations with anomalies to produce smaller, well-structured relations.

36. Functional Dependencies and Keys
Functional Dependency: The value of one attribute (the determinant) determines the value of another attribute.
Candidate Key: Each non-key field is functionally dependent on every candidate key.
Fig

37. Steps in normalization

38. First Normal Form No multi-valued attributes.
Every attribute value is atomic.
Fig. 6-2a, b.

39. Second Normal Form
1NF and every non-key attribute is fully functionally dependent on the primary key.
Every non-key attribute must be defined by the entire key, not by only part of the key.
No partial functional dependencies.
Fig. 6-2b, 6-22b.

40. Third Normal Form
2NF and no transitive dependencies (functional dependency between non-key attributes.)
Fig. 6-23, 6-24, 6-25.

41. Relation with transitive dependency
(a) SALES relation with simple data

42. (b) Transitive dependency in SALES relation

43. Removing a transitive dependency
(a) Decomposing the SALES relation

44. (b) Relations in 3NF

45. Merging Relations (View Integration)
Synonyms: Different names, same meaning.
Homonyms: Same name, different meanings.
Transitive Dependencies: e.g. (Stu ID, Major) (Stu ID, Advisor).
Supertype/Subtype.