Group a transfer in a transaction
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.
Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.
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
The provided transfer opens BEGIN, checks inputs, subtracts 3 from A, adds 3 to B, checks total 10 and COMMITs.
A transaction defines an all-or-nothing unit. BEGIN starts it; COMMIT accepts the complete valid change; ROLLBACK discards it. This course uses a single fresh SQLite connection, not a proven production concurrency design.
Group a transfer in a transaction — original worked practice
A transaction defines an all-or-nothing unit. BEGIN starts it; COMMIT accepts the complete valid change; ROLLBACK discards it. This course uses a single fresh SQLite connection, not a proven production concurrency design.
The provided transfer opens BEGIN, checks inputs, subtracts 3 from A, adds 3 to B, checks total 10 and COMMITs.
1. Step 1
Run make_database in a fresh process.
You should see: A 8, B 2 is recreated as fictional state.
This keeps the rule and its observable result together.
2. Step 2
Read the BEGIN and COMMIT boundary.
You should see: Both updates belong to the same transaction.
This keeps the rule and its observable result together.
3. Step 3
Trace before and after total queries.
You should see: They both return 10 for success.
This keeps the rule and its observable result together.
4. Step 4
Run transactions.py and inspect A 5, B 5.
You should see: A committed all-or-nothing transfer record.
This keeps the rule and its observable result together.
What to finish
A committed all-or-nothing transfer record.
Watch for this
Committing the subtraction before adding to the destination, leaving a half-finished transfer.
How can I tell I understand it?
Explain and demonstrate the required distinction: A transaction defines an all-or-nothing unit. BEGIN starts it; COMMIT accepts the complete valid change; ROLLBACK discards it. This course uses a single fresh SQLite connection, not a proven production concurrency design. Show a changed input and the expected result without weakening this contract.
Quick knowledge check
Answer all 3 questions. Get at least 2 right and the lesson completes automatically.
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Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.
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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.
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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