<ul class="roh-list">
<?php
        $sql = "
        SELECT DISTINCT(category) AS category FROM mytable WHERE subject = 'animals' && subcat = 'cats'
        ";

$results = $db->query($sql);

if($results->num_rows) {
    While($row = $results->fetch_object()) {
        echo "

    <li><a href='categories/{$row->thing}/roh-index.php'>{$row->category}</a></li>


";
    }
} else {
    echo 'No Results';
}
?>
</ul>