DB query in Revolution?

$this->allGroups = array ();  // Create an array of group names from the MODx db
            $tableName = $modx->getFullTableName('webgroup_names`);
            echo "Full Table Name: ".$tableName;  // I get the correct table name here

            $sql = "SELECT name FROM $tableName";
            if ($rs = $modx->db->query($sql)) {
                while ($row = $modx->db->getRow($rs)) {
                    $this->allGroups[] = stripslashes($row['name']);
                }
            } else {
                echo "Query Failed\n"; // this is all I get
                print_r($rs);   // prints nothing.
          
            }

if ($rs = $modx->query("SELECT name FROM {$modx->getTableName('modWebGroup')}")) {
    $allGroups= $rs->fetchAll(PDO_FETCH_COLUMN);
}

$webgroups= $modx->getCollection('modWebGroup');
foreach ($webgroups as $group) {
    $allGroups[]= $group->get('name');
}

 $sql = "SELECT name FROM $tableName";

 $sql = "SELECT name FROM ". $tableName;

            $sql = "SELECT name FROM ".$tableName;
            if ($rs = $modx->db->query($sql)) {
                while ($row = $modx->db->getRow($rs)) {
                    $this->allGroups[] = stripslashes($row['name']);
                }
            } else {
                echo "Query Failed\n";
                return '';
            }