Fetching only first row from database I work with:

$mandator = $this-&gt;database-&gt;select('Mandators', 'm')
     -&gt;fields('m')
     -&gt;condition('idMandators', $mandatorId)
     -&gt;execute()
     -&gt;fetchAll();


to retrieve my data from database. The result is an array with 1 array item. How can I retrieve always only 1 object, without the array? Like e.g. -&gt;fetchOne?
$query = \Drupal::entityQuery('node')
            -&gt;condition('status', 1)
            -&gt;condition('type', 'my_content_type')
            -&gt;condition('field_ref_au', $nid, '=')
            -&gt;range(0,1)
            -&gt;sort('created', 'DESC')
        ;