PDO exceptions carry the SQL error code. However DBALException doesn't forward any error code from the SQL exception.

Here is a (really poor/quick) example of usage:

try {
    $em->flush();
} catch (DBALException $e) {
    if ($e->getCode() === 23000) {
        echo '';
    } else {
        throw $e;
    }
}

I think I found where the problem is:

public static function driverExceptionDuringQuery(\Exception $driverEx, $sql, array $params = array())
{
    $msg = "An exception occurred while executing '".$sql."'";
    if ($params) {
        $msg .= " with params ".json_encode($params);
    }
    $msg .= ":\n\n".$driverEx->getMessage();

    return new self($msg, 0, $driverEx);
}

In return new self($msg, 0, $driverEx);, the exception is created with an error code of 0.

Is there a reason for this: is that that the driver exception may not always have a defined error code? (for example if the sql driver is not PDO or the SQL system doesn't support that, but in this case then the error code would be 0 would that be a problem?)