## BC BREAK Transaction-related `Statement` methods return `void`.
`Statement::beginTransaction()`, `::commit()` and `::rollBack()` no longer return a boolean value. They will throw a `DriverException` in case of failure.
## MINOR BC BREAK `Statement::fetchColumn()` with an invalid index.
Similarly to `PDOStatement::fetchColumn()`, DBAL statements throw an exception in case of an invalid column index.