Question
consider the following action transaction SQL>Commit;
SQL>Rollback;
What does rollback can do in the above statement?
SQL>Rollback;
What does rollback can do in the above statement?
Answers
GPT-4o mini
In SQL, a `ROLLBACK` statement is used to undo any changes made to the database during the current transaction. A transaction is a sequence of one or more SQL operations that are executed as a single unit of work.
From your provided statements:
```sql
SQL> Commit;
SQL> Rollback;
```
Here's what happens:
1. **Commit**: When you issue a `COMMIT`, it finalizes all changes made in the current transaction. Once a transaction has been committed, all changes made during that transaction are permanently saved to the database.
2. **Rollback**: In the context of your given statements, after a `COMMIT` has been executed, issuing a `ROLLBACK` does not have any effect on the changes made during that transaction. The database state cannot go back to before the `COMMIT`; hence the `ROLLBACK` would typically generate an error indicating that there is no active transaction to roll back.
In summary, after a `COMMIT`, a `ROLLBACK` is essentially a no-op (no operation) because no changes are eligible to be undone. If you want to roll back changes, you must do so before issuing a `COMMIT`.
From your provided statements:
```sql
SQL> Commit;
SQL> Rollback;
```
Here's what happens:
1. **Commit**: When you issue a `COMMIT`, it finalizes all changes made in the current transaction. Once a transaction has been committed, all changes made during that transaction are permanently saved to the database.
2. **Rollback**: In the context of your given statements, after a `COMMIT` has been executed, issuing a `ROLLBACK` does not have any effect on the changes made during that transaction. The database state cannot go back to before the `COMMIT`; hence the `ROLLBACK` would typically generate an error indicating that there is no active transaction to roll back.
In summary, after a `COMMIT`, a `ROLLBACK` is essentially a no-op (no operation) because no changes are eligible to be undone. If you want to roll back changes, you must do so before issuing a `COMMIT`.