use Drupal\webform\Entity\Webform;

    use Drupal\webform\Utility\WebformOptionsHelper;

​

    // get the submissions

    $submissions = array();

    $select = \Drupal::service('database')

      ->select('webform_submission_data', 'wsd')

      ->fields('wsd', array('sid'))

      ->orderBy('wsd.sid', 'DESC')

      ->condition('wsd.webform_id', 'my_form_id', '=')

      ->execute();

​

    // Get all the results.

    $results = $select->fetchAll(\PDO::FETCH_COLUMN);

    if ($results != null && count($results) >= 1) {

      $storage = \Drupal::entityTypeManager()->getStorage('webform_submission');

      $submissions = $storage->loadMultiple($results);

    }

​

    // Load the webform using webform machine name

    $webform = Webform::load('my_form_id');

​

    foreach ($submissions as $submission) {

​

      // select field processing

      // Get the submission data for the select field (returns the keys no the values)

      $select_submission_data = $submission->getElementData('my_select_field');

​

      // Get the element definition

      $select_list_element = $webform->getElement('my_select_field');

​

      // Get the options from the element via $element['#options]

      $select_list = select_list_element['#options'];

​

      // get value from key

      $select_list_value = $select_list[$select_submission_data];

​

      // multiselect checkboxes field processing

​

      // get the submission data for the multiselect field (returns the keys)

      $multiselect_submission_data = $submission->getElementData('my_multiselect_field');

​

      // Get the multiselect element definition

      $multiselect_list_element = $webform->getElement('my_multiselect_field');

​

      // Get the options from the multiselect element via $element['#options]

      $multiselect_list = $multiselect_list_element['#options'];

​

      // Look up the options values

      $multiselect_list_values = WebformOptionsHelper::getOptionsText($multiselect_submission_data, $multiselect_list);

    }