Question

I have a table like following

well,here in this table every user has a parent user,then if we select a user then its id ,children ids and children childrens ids should return as array.I need a query to get this values in rails with out using any gem.Thanx for your help:->

Answer 1

class User << ActiveRecord::Base      
  def self.build_tree(reverse=false)
    g = Array.new    
    self.find(:all).each do |p|           
        if reverse
        g << [p.id,p.parent]            
        else
        g << [p.parent,p.id]            
        end
    end
    g
  end
  def self.subordinates(man_id)
    g = self.build_tree false       
    g.map{|i| i[1] if i[0]==man_id.to_i}.compact    
  end
  def self.superiors(user_id)
     g = self.build_tree true            
     g.map{|i| i[1] if i[0]==user_id.to_i}.compact     
  end
end

When call either Superiors(parents) or Subordinates(childrends) it will gives required result
Ex:- [2,4,6,8]
If you want to get either children->childrends or parent->parents just do iterate call function either superior or subordinates until get the nil or [] array .