public function getTableAlias($table_name = null)
    {
        if (!$table_name) {
            $table_name = $this->getTableName();
        }
        $bits = explode("_", $table_name);
        $alias = '';
        foreach ($bits as $bit) {
            $alias .= strtolower(substr($bit, 0, 1));
        }
        return $alias;
    }