Sommario
Conceptual Design Using the Entity-Relationship (ER) Model
Overview of Database Design
ER Model Basics
ER Model Basics (Contd.)
ER Model Basics (Contd.)
Key Constraints
Translating ER Diagrams with Key Constraints
Participation Constraints
Cardinality Constraints
Participation Constraints in SQL
Weak Entities
Translating Weak Entity Sets
ISA (`is a’) Hierarchies
Translating ISA Hierarchies to Relations
Aggregation
Conceptual Design Using the ER Model
Entity vs. Attribute
Entity vs. Attribute (Contd.)
Entity vs. Relationship
Binary vs. Ternary Relationships
Binary vs. Ternary Relationships (Contd.)
Binary vs. Ternary Relationships (Contd.)
Constraints Beyond the ER Model
Summary of Conceptual Design
Summary of ER (Contd.)
Summary of ER (Contd.)
Design Methodologies
Top-down
Bottom-up
Mixed
Conceptual Schema Qualities
Top-down example
First Refinements
Other Refinements
Final Refinements
Final schema
Bottom-up
Choice of Entities
ISA
Attribute Restructuring
Relationships
From Conceptual to Logical
Restructuring
Redundancies
Transactions
Time and memory changes with redundancies
IS-A Hierarchy Translation
Merging vs. Splitting
Comparison of Transaction Accesses
Integrity Constraints
Other solutions
Entities Partitioning and Merging
Merging
Primary Keys
Translation
Notes
|