Entity Query field condition for Webform submissions
As imclean says webform_submission_data stores as EAV model. You can also do the following, If you need to have just one condition ticket_for == $adnummer.

$select = \Drupal::service('database')
-&gt;select('webform_submission_data', 'wsd')
-&gt;fields('wsd', array('sid'))
-&gt;orderBy('wsd.sid', 'DESC')
-&gt;condition('wsd.webform_id', 'your_webform_id', '=')
-&gt;condition('wsd.name', 'ticket_for', '=')
-&gt;condition('wsd.value', $adnummer, '=')
-&gt;execute();

$results = $select-&gt;fetchAll(\PDO::FETCH_COLUMN);
if ($results != null &amp;&amp; count($results) &gt;= 1) {
    $storage = \Drupal::entityTypeManager()-&gt;getStorage('webform_submission');
    $submissions = $storage-&gt;loadMultiple($results);    
}


Now just loop the $submissions. Done.