I want to count the number of submissions where formid is 16, state is mystate1, qda is myqad1 , and city is mycity1.

In my example, the count should be 1 because only SubmissionId number 2 satisfies all requirements.

$query = $db->getQuery(true);
//$query->select('COUNT(*)');
$query->select($db->quoteName('FieldValue') . ' IN ("mycity1")');

$query->from($db->quoteName('#__rsform_submission_values'));
$query->where($db->quoteName('formid') .' IN ("16")');
$query->where($db->quoteName('FieldName') .' IN ("state","qda","city")');
$query->where($db->quoteName('FieldValue') . ' IN ("mystate1","myqad1","mycity1")');
$db->setQuery($query);
$results = $db->loadObjectList();

foreach($results as $value) {
    foreach($value as $key => $data) {
        echo $data."<br />";
    }
}

Here's my attempted query, but it doesn't produce the count that I want:

SELECT COUNT(SubmissionId)  
FROM my_submission_values 
WHERE FormId = '16' 
   AND FieldName ='state' 
   AND FieldValue = 'mystate1' 
   AND FieldName = 'qda' 
   AND FieldValue = 'myqad1' 
   AND FieldName = 'city' 
   AND FieldValue ='mycity1'