Active Record a stavění dotazů

gistfile1.rb

class Site < ActiveRecord::Base

  def self.build_conditions(ids, name=nil, state=nil)
     cond = []
     cond << send(:sanitize_sql_array, ["id NOT IN (?)", ids]) unless ids.empty?
     cond << send(:sanitize_sql_array, ["name = ? ", name]) unless name
     cond << send(:sanitize_sql_array, ["state = ? ", state]) unless state
     cond.join(" and ")
  end    
end
Now somewhere in your controller:

Site.all(:conditions => Site.build_conditions([1,2])) 
Site.all(:conditions => Site.build_conditions(nil, "ABC"))