Software Engineering › Key terms › Diagrams and tools › Entity relationship diagram (ERD)
Entity relationship diagram (ERD)
Diagram Check Diagrams and tools
Definition
Shows the tables (entities) in a database, their attributes and the relationships between them (one-to-one, one-to-many, many-to-many) using primary and foreign keys.
Example: Customer 1 to many Order.
Check this one: Your school's drawing-questions page says the ERD is technically NOT in the syllabus (practice only); the course specification has no ERD symbols. Learn it as a low priority.
Found in: school notes.
Where it is used in the test
Syllabus area: Diagrams and tools.
Question types it can appear in
- Drawing: Draw an ERD
- Short answer: Define, outline or explain it and tie it to the scenario.
- Multiple choice: Pick the option that matches the definition or example.
No past question in this bank is linked to this term yet. It can still be tested through the question types above.
Study links
- Flashcard: Entity relationship diagram (ERD) in Diagrams and Modelling Tools (Years 11 and 12) · study that set
- Memorise: Drawing rules: DFD, structure chart, storyboard, decision tree, class diagram, ERD
- Notes: Modelling tools: DFD, structure charts, storyboards, flowcharts, class diagrams (The Software Engineering Project (Year 12))
- Notes: Drawing rules: DFD, structure chart, storyboard, decision tree, class diagram, ERD (Pseudocode, flowcharts and diagram rules)
- Notes: SQL: HSC syntax and must-know queries (Python and SQL you must be able to write)
- Master answer: skel-draw | Technique: drawing questions (DFD, flowchart, structure chart, class… (Master model answers: how to use)
How to use it in an answer
A model sentence
Diagram: “Shows the tables (entities) in a database, their attributes and the relationships between them (one-to-one, one-to-many, many-to-many) using primary and foreign keys.” Then apply it: Customer 1 to many Order.
In a short answer, give the definition in your own words first, then tie it to the situation in the question. Do not copy the example above unless it fits the scenario.
Command words used with it
No linked question shows the command word for this term. Across the past drawing and short answer questions in this bank the words used most are: Explain, Outline, Describe, Compare, Classify, Analyse. Check the actual word in your question.
Technique for the question types
- Drawing: Use the online drawing tool: label every symbol and arrow, use the correct symbols from the specification, and add every required item.
- Short answer: One clear point per mark, use the stimulus and course terms, and answer the command word.
- Multiple choice: Read all four options, rule out wrong ones, pick one; no penalty for guessing so never leave blank.
Common mistakes
- Check the sources: Your school's drawing-questions page says the ERD is technically NOT in the syllabus (practice only); the course specification has no ERD symbols. Learn it as a low priority.
- Drawing questions (2025 HSC exam Q22): refine attributes into separate inherited classes; use appropriate class diagram symbols.
- Use the term exactly as the syllabus words it, then link it to the scenario in the question; the 2025 feedback repeatedly rewards using the stimulus.
- Answer the command word: outline gives main points only, explain gives a reason or cause, discuss gives both sides.
Related terms
Same group in the syllabus: Class diagram · Class diagram inheritance and multiplicity · Storyboard · Decision tree · Data dictionary · Gantt chart · Process diary (log book) · Wiring diagram · Flowchart · Mainline and subroutines (algorithms)