ISMT221 Information Systems Analysis and Design Entity-Relationship Diagram Lab 4 Tony Tam

Agenda Presentation About Entity-Relationship Diagram Explaining the ERD Build up some fundamental information Your turn Setup environment for ERD Draw a very simple ERD Practice on narrative text ERD drawing

Entity-Relationship Diagram Conceptual data model of the data (data store) Logical data model Independent of the physical data model i.e. I can use different physical database (e.g. Oracle, SQL Server, Sybase) with the same conceptual data model Works together with DFD to give a full picture of the whole system

Entity-Relationship Diagramming Crow’s Foot Notation Relationship with Foot Cardinality Minimum cardinality Minimum number of instances (0) Maximum cardinality Maximum number of instances (many) Minimum is ZERO Maximum is MANY

Explaining ERD PK – primary key FK# - foreign key (reference key) Bolded attributes – Mandatory field The relationship read as: 0:M Student belongs to 1:1 major 1:1 Major is composed of 0:M Student Must be active verb Must be singular

What are they? Candidate Key All available unique, required identifiers of an entity Primary Key A unique, required identifier of an entity The best one of candidate keys Foreign Key A reference key to another entity This key is the primary key of another entity