CS 320: Database Management Systems

The Relational Data Model

Ge (Frank) Xia, CS, Lafayette College

Contents

A Relation is a Table

Schemas


Why Relations?

From E/R Diagrams to Relations

Entity Set -> Relation

Relationship -> Relation

Combining Relations

Risk with Many-Many Relationships

Handling Weak Entity Sets

Example


Subclasses: Three Approaches

Example

Object-Oriented

E/R Style

Using Nulls