有一些has_many通过查询的问题.
使用此处的示例：http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association
class Physician < ActiveRecord::Base has_many :appointments has_many :patients,:through => :appointments end class Appointment < ActiveRecord::Base belongs_to :physician belongs_to :patient end class Patient < ActiveRecord::Base has_many :appointments has_many :physicians,:through => :appointments end
Appointment表有一个名为appointment_date的列
如何让特定医师的所有患者在指定日期预约？
解决方法
Patient.includes(:physicians,:appointments).where('physicians.id = ? AND appointments.appointment_date = ?',<id or ids array>,Date.today)
Date.today可以用任何东西改变,而pysician由id或一组id指定.
你也可以这样做：
physician = Physician.find(id)
patients = physician.patients.includes(:appointments).where('appointments.appointment_date = ?',some_date)
编辑：