INFO 340 - Entity Relationships
Notes By: Egaas, Fortier, Prins

Introduction to Entity Relationship Modeling:

Modeling allows you to break apart your problem domain

Design leads to a model:
    Sketching
    Prototyping
    Specification

> Attributes are listed beneath entity
> {PK} means primary key
> Composite attributes (indented)

Degree of Relationship: Binary
    > The number of entities that participate in a relationship
    > Binary
        - "Branch has Staff"

Degree of Relationship: Unary
    > Unary (recursive)
        - "Staff supervises staff"
    > Other examples?

Database Implementation
    > Part(id: integer; parent: integer, pname:string)
    > Primary Key
        - id
    > Foreign Key
        - parent
        
What Does this Do?
    > SELECT * FROM Part WHERE parent_id = 0;
        - It would get the 1st level of the hierarchy from the previous slide

Degree of Relationship
    > Ternary
        - "Staff registers a client at a branch"
    > Quaternary
        - "A solicitor arranges a bid on behalf of a buyer supported by a financial institution."

Attribute Types
    > Attributes are listed beneath each entity
    > {PK} mean primary key
    > /derived attribute value (global variable per se)
    > Composite attributes (indented)
    > Multi-Valued attributes [1..3]

Weak: Exists in the presence of another entity (strong)
Strong: Can stand on its own