[`BEGIN`] starts a transaction block. Once a transaction is started:

- Statements within the transaction are executed sequentially.

- A transaction ends with either a [`COMMIT`] or a
  [`ROLLBACK`] statement.

  - If all transaction statements succeed and a [`COMMIT`] is issued, all
    changes are saved.

  - If all transaction statements succeed and a [`ROLLBACK`] is issued, all
    changes are discarded.

  - If an error occurs and either a [`COMMIT`] or a [`ROLLBACK`] is issued,
    all changes are discarded.