← ACARA Digital Technologies Years 7–8

Deleting data that is no longer needed

Keeping data only as long as its purpose needs it, then deleting it, including old accounts, finished project data and backup copies.

Part of: ACARA Digital Technologies Years 7–8 — Digital Footprints and Data Minimisation — Module 27, WA Computer Science ATAR Year 11 — Data Management — Module 104

Understanding Deleting data that is no longer needed in ACARA Digital Technologies Years 7–8

What it does: Once the project is over, its data has no purpose, so the old rows are deleted using a date condition. Deleting only the main file leaves the personal data in the backup, so every copy must be removed. Old accounts still store personal data. If the account is hacked or leaked, that data is at risk, so delete accounts you no longer use. The purpose was running the membership. When it ends, the details should be deleted, not reused for a new purpose.

Common mistakes: The data should only be deleted once the project has finished and its purpose is over. It should be IF project = 'finished' THEN. A project that is only starting still needs its data. An account that has not been used for years no longer has a purpose, so it should be deleted. The line should be DELETE acc, not KEEP acc.

Class: _____________________ · Name: _____________________ · Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

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This module's key terms are also in a printable crossword (Modules 728–751) and word search (Modules 696–770).

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Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

A school finishes a sports carnival. The signup sheet with student phone numbers is no longer needed. What should happen to it?

Keep it forever in case it is useful one dayDelete it, because its purpose has ended

Matches

Delete survey.xlsx but keep survey_backup.xlsx forever

↓

The backup copy still holds the same personal data, so the data has not really been deleted.

Applying

Meanings

Term

data retention

Meaning

Keeping data only as long as its purpose needs it, then deleting it, including old accounts, finished project data and backup copies.

Practice

DELETE FROM orders WHERE orderDate < '2026-02-04';

Testing

Gaps

FROM orders WHERE orderId = 3;

Check Answer

Spots

1IF project = 'starting' THEN

2 DELETE survey_answers

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Quick Questions

1. A school finishes a sports carnival. The signup sheet with student phone numbers is no longer needed. What should happen to it?

A. Delete it, because its purpose has ended ✓

B. Keep it forever in case it is useful one day

Data retention means keeping data only as long as its purpose needs it. When the carnival is over, the signup sheet should be deleted.

2. Which statement describes data retention?

A. Keeping data only as long as its purpose needs it, then deleting it ✓

B. Keeping all data for as long as possible just in case

Good data retention has an end point. Once the purpose is finished, the data is deleted.

3. You have not used a game account for three years. It still holds your name, email and birthday. What is the best choice?

A. Leave it, because unused accounts hold no risk

B. Delete the account so the old data is removed ✓

Old accounts still store personal data. If the account is hacked or leaked, that data is at risk, so delete accounts you no longer use.

4. Your team finishes a class project that collected survey answers. When should the raw survey data be deleted?

A. Never, because the data might be handy later

B. Once the project is finished and the data is no longer needed ✓

The purpose of the survey data ends with the project. Keeping it longer adds risk and has no benefit.

5. You delete a spreadsheet of names from your main folder, but a backup copy is still stored in cloud storage. Is the data fully deleted?

A. No, the backup copy still holds the data ✓

B. Yes, deleting the main file removes every copy

Backup copies also hold data. To finish deleting, you must remove the backups too.

Match the Pairs

data retention → Keeping data only as long as its purpose needs it, then deleting it

DELETE FROM students WHERE studentId = 7; → Removes one old record that is no longer needed

When a school project ends, delete the survey responses you collected for it → DELETE FROM orders WHERE orderDate < '2026-02-01';

Backup copies also hold data, so they must be deleted too, not just the main file → delete survey.xlsx and delete survey_backup.xlsx

Delete survey.xlsx but keep survey_backup.xlsx forever → The backup copy still holds the same personal data, so the data has not really been deleted.

Keep an old account open for years 'just in case' → The account has no current purpose, so its data should be deleted instead of kept for no reason.

Key Term

data retention

Keeping data only as long as its purpose needs it, then deleting it, including old accounts, finished project data and backup copies.

Fill in the Blanks

1. DELETE FROM orders WHERE orderId = 3;

Hint: Type the SQL command that removes a row of data that is no longer needed.

2. IF projectFinished THEN DELETE surveyData END IF

Hint: Type the keyword that starts the action to run once the project is over.

3. backup = copy(surveyData) DELETE surveyData DELETE backup

Hint: Type the variable that holds the extra copy of the data, which must be deleted too.

4. IF lastLogin < oneYearAgo THEN DELETE account END IF

Hint: Type the comparison operator meaning earlier than, so old unused accounts are found.

5. DELETE FROM orders WHERE orderId < 5;

Hint: Type the SQL keyword that limits which old rows get deleted.

Spot the Error

Question 1

A IF project = 'starting' THEN

B DELETE survey_answers

C END IF

Line A — The data should only be deleted once the project has finished and its purpose is over. It should be IF project = 'finished' THEN. A project that is only starting still needs its data.

Question 2

A FOR EACH acc IN accounts

B IF unused_years > 2 THEN

C KEEP acc

D END IF

E NEXT

Line C — An account that has not been used for years no longer has a purpose, so it should be deleted. The line should be DELETE acc, not KEEP acc.

Question 3

A DELETE FROM accounts

B WHERE active = 'yes';

C SELECT COUNT(*) FROM accounts;

Line B — This would delete the accounts people are still using. The old accounts to remove are the inactive ones, so it should be WHERE active = 'no';.

Question 4

A SET limit TO 30

B FOR EACH copy IN backups

C IF copy.age < limit THEN

D DELETE copy

E END IF

Line C — The comparison is the wrong way round, so it would delete the newest backups and keep the old ones. It should be IF copy.age > limit THEN. Backup copies also hold data and must be deleted when they are too old.

Question 5

A project_finished = True

B survey_data = ['a1', 'a2']

C if project_finished:

D survey_data.clear

Line D — The brackets are missing, so clear is never called and nothing is deleted. It should be survey_data.clear() to remove the data when the project is finished.

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