public function getTablePk($tableName) {
        $details = $this->getTableColumns($tableName);
        $pk = [];
        foreach ($details as $column) {
            if ($column['Key'] == 'PRI') {
                $pk[] =  $column['Field'];
            }
        }
        if (1 == count($pk)){
            return $pk[0];
        } elseif (count($pk)) {
            return $pk;
        }
        return null;
    }