ROLLBACK is a command that can bring the state of the data a step back, but not more than that. It will refer to the state corresponding to the last time you executed COMMIT. This means if you have already used COMMIT 10 times, ROLLBACK will have an effect on the last execution you have performed. After that moment, even if you run the ROLLBACK clause 20 times, you can get to the state of only the last COMMIT. You cannot restore data to a state corresponding to an earlier COMMIT.
