外鍵, :joins, :conditions(2) :include

@tasks = Task.find(:all,
                              :include => :goal 
                              :conditions => "goals.name = 'abc' ")

Rails 提供了:include 這樣的選擇, 使用:include選項時在其他參數(如conditions)用到欄位名稱(如name)時,就要加上table name(goals)這樣它才知道正確的查詢