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Software Engineering › Key terms › Y12 Programming for the Web › SQL GROUP BY

SQL GROUP BY

Code pattern Y12 Programming for the Web

Definition

Groups rows that share a value so aggregate functions (COUNT, SUM, AVG, MIN, MAX) can be applied to each group.

Example

SELECT class, COUNT(*) FROM students GROUP BY class;

Found in: syllabus, course specifications, 2025 HSC marking guidelines, school notes.

Where it is used in the test

Syllabus area: Y12 Programming for the Web.

Question types it can appear in

Where it has appeared in the paper

Programming for the Web (Part A, B). Part letters follow each paper’s own layout.

Related past questions

These are the questions the flashcard set links to this term. Open each one and compare your answer with its marking criteria.

Study links

How to use it in an answer

A model sentence

General advice, built from the definition and example above

Code pattern: “Groups rows that share a value so aggregate functions (COUNT, SUM, AVG, MIN, MAX) can be applied to each group.” Then apply it: SELECT class, COUNT(*) FROM students GROUP BY class;

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.

Technique for the question types

What the marking guidelines and feedback say

2025 HSC Q21 (4 marks): SQL queries

Note: the sample does not filter Category to Software/Hardware (the table is assumed to have only those two). Adding AND (Category = 'Software' OR Category = 'Hardware') is safe. Marker feedback: query must run; quotation marks around data being searched; use OR/AND in WHERE; correct GROUP BY and ORDER BY fields.

Worked answers from the marking guidelines

2025 HSC Q21 (4 marks): SQL queries (4 marks): criteria and sample answer

Criteria

4: Correct SQL query that extracts 'Pending' and 'Escalated' jobs for the 'Software' and 'Hardware' categories, counts the jobs for each status in each category, and outputs results in descending order. 3: Addresses most requirements. 2: Some understanding of the problem. 1: Some understanding of SQL or the problem.

Sample answer

SELECT Category, Status, COUNT(JobID) AS Jobs FROM Issues WHERE (Status = 'Pending' OR Status = 'Escalated') GROUP BY Status, Category ORDER BY Jobs DESC

Open the question page

Sample exam Q22a (2 marks): SQL (GROUP BY) (2 marks): criteria and sample answer

Criteria

2: Correctly completes the SQL query. 1: Correctly selects at least TWO correct options.

Sample answer

SELECT Level, COUNT(StudentID) FROM Students GROUP BY Level;

Open the question page

Common mistakes

Marker feedback on other questions of the same type (code and diagram feedback often applies across questions)
  • SQL questions (2025 HSC exam Q21): query must run; quotation marks around data being searched; use OR/AND in WHERE; correct GROUP BY and ORDER BY fields.
General advice
  • 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.

Same group in the syllabus: Shell commands (mkdir, cd, touch, cp, rm, cat, grep) · SQL SELECT · SQL WHERE · SQL ORDER BY · SQL aggregate functions (COUNT, SUM, AVG) · SQL JOIN · SQL alias (AS) · SQL constraints · Primary key and foreign key · Object-relational mapping (ORM) · Service worker · Web app manifest · CRUD

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