ER Modeling (Advanced) - L2

Flashcards for Week 2 Lecture: ER Modelling (Advanced)

Entity-Relationship Modeling

A modeling technique used in database design.

Crow’s Foot notation

A visual representation standard used in database design, as specified in the textbook.

Attribute

A characteristic or property of an entity.

Relationship Degree

The number of entities associated with a relationship.

Logical Model

Converting Conceptual model to detailed Logical Model ready for DB implementation.

Weak Entity

An entity that cannot exist without another parent entity.

Strong Entity

An entity that can exist apart from parent entities.

Strong (identifying) relationships

Relationships where the primary key of the child entity contains a primary key component of the parent entity.

Weak (non-identifying) relationship

Relationships where the primary key of the child entity does not contain a primary key component of the parent entity.

Composite Entity

An entity that builds a bridge between original entities and contains attributes singular to the relationship.

M:N relationships

Relationships where many instances of one entity can relate to many instances of another entity.

1:M relationships

Relationships where one instance of an entity relates to many instances of another entity.

Supertype

A more generic entity type.

Subtype

A more specific entity type compared to its supertype.

Specialisation Hierarchy

Depicts arrangement of higher-level supertypes and lower-level subtypes

Generalisation Process

Defining a general entity type from a set of specialised entity types

Specialisation Process

Defining one or more subtypes of the supertype

Disjoint (non-overlapping) subtypes

Contain a unique subset of the supertype entity set.

Overlapping subtypes

Contain non-unique subsets of the supertype entity set

Convert Logical Model to Relational Model

Relational Modelling and SQL

Natural key

Real-world, generally accepted identifier for real-world objects