gistfile1.rbx

class Patient < ActiveRecord::Base
  has_many :documents
  has_many :reports, :through => :documents do
    def find_for_parameter(parameter)
# report hm parameters
      find(:all, :joins => :parameters, :conditions => ['parameters.id = ?', parameter.id])
    end
  end

# @patient.reports.find_for_parameter(Parameter.first)
# SELECT  `reports` . * 
# FROM  `reports` 
# INNER JOIN documents ON ( reports.document_id = documents.id ) parameters
# WHERE (
# documents.patient_id =1
# AND (
# parameters.id =14
# )
# )