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Mastering Entity-Relationship Diagrams: ERD Fundamentals and Practice

Learn Entity-Relationship Diagram concepts, build simple ERDs, practice narrative text drawing, model data, and understand cardinality. Explore PK, FK, candidate keys, and the importance of data modeling. Discover how ERDs work with DFDs for system analysis.

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Mastering Entity-Relationship Diagrams: ERD Fundamentals and Practice

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  1. ISMT221Information Systems Analysis and Design Entity-Relationship Diagram Lab 4 Tony Tam

  2. 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

  3. 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

  4. 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) Maximum is MANY Minimum is ZERO

  5. 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

  6. 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

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