code: public function getColumn($query, array $arguments = array(), $column_number = 0)
    {
      return $this->run($query, $arguments)->fetchColumn($column_number);
    }
docs: PDO::prepare()::execute()::fetchColumn() chaining wrapper.
  
  @param string SQL query with placeholders.
  @param array substitution variables.
  @param int column number to retrieve value from.
  @return mixed value of the $column_number's column from the first row of the resultset.
  
  @see PDO::prepare()
  @see PDOStatement::execute()
  @see PDOStatement::fetchColumn()