问题描述
通过查询使用 has_many 时遇到一些问题.
Having some problems with a has_many through query.
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
约会表有一列名为appointment_date
我如何从特定医生那里获得在给定日期有预约的所有患者?
How would I get all the Patients from a Specific Physician that have an appointment on a given date?
推荐答案
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，医生是由一个 id 或一组 id 指定的.
Where Date.today could be changed with anything and the pysician is specified by an id or an array of ids.
你也可以这样做:
physician = Physician.find(id)
patients = physician.patients.includes(:appointments).where('appointments.appointment_date = ?', some_date)
在 Rails 4 及更高版本中，您需要将 references(:appointments) 添加到查询中，以便在 where 子句中使用约会.
In Rails 4 and forward, you need to add references(:appointments) to the query in order to use appointments in the where clause.
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