Consider the following transaction:

START TRANSACTION;
INSERT INTO Product VALUES (G43547, "Gucci", "BAMBOO 1947 MINI BAG", 5840, 4300);
UPDATE Product SET RetailPrice = RetailPrice * 0.95;
COMMIT;
ROLLBACK;

What will be the result of Rollback in the code above?

Question

Consider the following transaction:

START TRANSACTION;
INSERT INTO Product VALUES (G43547, "Gucci", "BAMBOO 1947 MINI BAG", 5840, 4300);
UPDATE Product SET RetailPrice = RetailPrice * 0.95;
COMMIT;
ROLLBACK;

What will be the result of Rollback in the code above?

BlackTom AI · Accepted Answer

COMMIT makes changes permanent, so a subsequent ROLLBACK has no effect on the already committed work.

1. Relevant knowledge points and concepts
- Transaction atomicity: a transaction groups multiple SQL statements so they either all succeed (commit) or all are discarded (rollback) while it is active.
- COMMIT finalizes and persists the effects of the current transaction to the database; after commit the changes are durable.
- ROLLBACK reverts the current, uncommitted transaction. If there is no active transaction (because it was already committed), ROLLBACK cannot undo prior committed changes.

2. Step-by-step reasoning process
- START TRANSACTION begins an explicit transaction context.
- INSERT INTO Product ... adds a new row but this change is still part of the active transaction (not yet visible to others depending on isolation).
- UPDATE Product SET RetailPrice = RetailPrice * 0.95 updates rows; these updates are also part of the active transaction.
- COMMIT writes (persists) all changes made in that transaction to the database and ends the transaction.
- ROLLBACK is executed after COMMIT. At this point there is no active transaction containing those prior statements.

3. Intermediate steps / state transitions
- After START TRANSACTION: transaction T1 active.
- After INSERT and UPDATE: T1 holds uncommitted changes (insert + price update).
- After COMMIT: T1’s changes are made permanent and transaction ends.
- After ROLLBACK: there is nothing left to roll back from T1 (either nothing happens or the DB returns “no transaction”); no changes are undone.

4. Why the correct answer is correct
Because COMMIT has already made the INSERT and UPDATE permanent, ROLLBACK cannot revert those committed changes. Therefore the ROLLBACK performs no action on those already committed statements.

5. Why other options are incorrect
- "It will undo all steps in the transaction after Commit": impossible because there are no uncommitted steps after commit.
- "It will undo all steps in the transaction before Commit": incorrect—ROLLBACK cannot undo steps already committed.
- "It will undo only the last step in the transaction": incorrect—ROLLBACK would revert the entire active transaction, not selectively one statement, and here there is no active transaction to revert.

6. Conclusion
The ROLLBACK will have no action/effect in this sequence. This confirms the provided correct answer: "No action."

Consider the following transaction: START TRANSACTION; INSERT INTO Product VALUES (G43547, "Gucci", "BAMBOO 1947 MINI BAG", 5840, 4300); UPDATE Product SET RetailPrice = RetailPrice * 0.95; COMMIT; ROLLBACK; What will be the result of Rollback in the code above?单项选择题

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