ROLLBACK a failed rule check
See this course’s project requirements
A local SQLite seat-transfer exercise with before/after totals, an all-or-nothing update, a deliberately rejected change and rollback evidence.
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What to include
- A seat-transfer contract with total 10 preserved.
- Two targeted updates with a declared completion boundary.
- A committed all-or-nothing transfer record.
- A 5, B 5 and no active transaction after rejection.
- A parameterized update/lookup record with known-ID validation.
- A checked seat-transfer transaction packet.
Review and revise
Use these criteria to check your work and choose what to improve.
- The implementation or declared simulation follows the supplied contract and retains inspectable original inputs.
- Normal, boundary and rejected cases are recorded with expected versus observed results.
- The changed case has a correct explanation and does not rely on hidden state.
- The project includes source, outputs, instructions and honest tool, privacy and verification limits.
Want more background?
The idea in everyday life
After a success A 5, B 5, attempt transfer 8 from A to B. The operation raises ValueError, and both remain 5.
ROLLBACK preserves the before state of a failed transaction. Validation and evidence both matter: inspect actual quantities after rejection rather than assuming an exception prevented all changes.
ROLLBACK a failed rule check — original worked practice
ROLLBACK preserves the before state of a failed transaction. Validation and evidence both matter: inspect actual quantities after rejection rather than assuming an exception prevented all changes.
After a success A 5, B 5, attempt transfer 8 from A to B. The operation raises ValueError, and both remain 5.
1. Step 1
Capture the before state A 5, B 5.
You should see: The valid previous result is retained.
This keeps the rule and its observable result together.
2. Step 2
Attempt the over-transfer.
You should see: Available 5 is less than requested 8; ValueError occurs.
This keeps the rule and its observable result together.
3. Step 3
Read the ROLLBACK exception branch.
You should see: The transaction is discarded.
This keeps the rule and its observable result together.
4. Step 4
Query both rows and transaction state after failure.
You should see: A 5, B 5 and no active transaction after rejection.
This keeps the rule and its observable result together.
What to finish
A 5, B 5 and no active transaction after rejection.
Watch for this
Catching an error without rolling back the already changed transaction.
How can I tell I understand it?
Explain and demonstrate the required distinction: ROLLBACK preserves the before state of a failed transaction. Validation and evidence both matter: inspect actual quantities after rejection rather than assuming an exception prevented all changes. Show a changed input and the expected result without weakening this contract.
Quick knowledge check
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Source & access notes · checked 2026-10-01
Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.
Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.
Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.
Source & access notes · checked 2026-10-01
Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.
Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.
Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.
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