1. Conceptual and Physical Database Design
Consideration of Implementation Details

2. Terminology Entity Field Attribute Record File Key field Primary Key
Minimal
Combination
Candidate
Nonkey field
Foreign key
Secondary key
See “Designing Fields,” p. 307.

3. Entity Relationship Diagrams
Entity - represented as a rectangle:
Attribute – represented as an oval:
Relationship - represented as a diamond:

4. ERDs (continued) Entity - singular noun Relationship - active verb
one-to-one
one-to-many
many-to-many

5. ERDs (still more) Cardinality Modality pertains to number
pertains to necessity of the entity’s participation in the relationship

6. Database Design Normalization
Progressively restrictive forms
Aim: flexibility and elimination of redundancy
Note: We will use the standard notation to show tables.

7. First Normal Form (1NF) 1NF record contains no repeating groups
may require use of combination key for primary key
see examples in text

8. Second Normal Form (2NF)
2NF record
is already in 1NF, and
every field in the record is dependent on the entire primary key.
Note that if the primary key of a 1NF record is a single field, then the record is in 2NF.
2NF is desirable
to promote database consistency,
to reduce overhead in adds, deletes, and changes

9. Creation of 2NF Records
To go from 1NF record with combination key to 2NF,
create a new record for each primary key field,
then for all combinations of primary key fields;
place each remaining field with the appropriate primary key (the minimal key),
then eliminate records having no nonkey fields.

10. Third Normal Form (3NF) A record is in 3NF if
it is in 2NF and no nonkey field is dependent on another nonkey field.

11. Other forms . . .
Boyce-Codd Normal Form - slightly more restrictive (stronger) than 3NF
if a non-key can determine another non-key, another relation should be formed
4NF - a key determines no more than one set of dependent values
5NF - beyond the scope of this course

12. More DBMS Terminology DDL Schema Subschema DML SQL QBE tuple
Data dictionary
DBA
data independence
consistency
redundancy
referential integrity
relation
attribute

13. Conceptual Database Models
Can you name them without looking at the book?

14. Conceptual Database Models
Hierarchical
Network
Relational
Object-oriented

15. Hierarchical Oldest Parent/child paradigm Disadvantages
1 parent : 1 or many children
Disadvantages
complex
data restructuring is painful

16. Network Defined by CODASYL Allows modeling of complex relationships
Preceded relational model
Efficient implementations delayed popular acceptance of relational model.
Data restructuring is painful

17. Relational Simple (relatively speaking) Flexible
Some changes to data base structure can be made without restructuring the entire data base.
Logical data independence is more readily achieved.

18. Relational Database Model
This is the predominant model today.
Database is like a collection of tables (relations).

19. Object-oriented
Relies on OO design
Still maturing

20. Files (terms) block logical record physical record organization access
master file
transaction file
blocking factor
buffer

21. Access Methods
Sequential
Direct (random)
Indexed sequential

22. File Organizations Sequential Relative Indexed sequential access only
random access only
Indexed
sequential or . . .
random

23. Database and/or File Design
DFD is a possible starting point.
Entity class diagram is a starting point.
Create an ERD.
Identify candidate keys.
Create 3NF record designs?
Consider access frequencies, data volumes, other factors.
Consider access methods.
Choose a database model and/or determine files.
Consider denormalization?