ActiveRecord::Base instances don't know how to dump themselves out as SQL. Here's a method to do so (tested only for PostgreSQL).

activerecord_base_to_sql.rb

class ActiveRecord::Base
  def to_sql
    columns = self.class.columns

    values_list = []
    columns.each do |column|
      value = self.__send__( column.name.to_sym )

      case column.type
        when :string, :text, :datetime, :timestamp, :time, :date
          unless value.nil?
            value = "'#{value}'".gsub( /([^'])'([^'])/ ){ |match| "#{$1}''#{$2}" }

            # PostgreSQL supports C-style string escape sequences like so:
            if /[[:cntrl:]]/ =~ value
              value.insert( 0, 'E' )
            end
          end
      end

      value = 'NULL' if value.nil?

      values_list << value
    end

    "INSERT INTO #{self.class.table_name} (#{columns.map(&:name).join(', ')}) VALUES (#{values_list.join( ', ' )});"
  end
end