Ruby has_many 使用 Postgres 数据库查询关联模型（Rails 5）

Question

我有模型，医生，有_many 患者。尝试编写一个查询，该查询只导致所有治愈患者的医生。因此，对于一个 Physician 的每个 Patient 都必须具有属性“is_cured: true”（或者至少对于所有 Physicians 患者来说不是 nil）。

目前为止有这个，但是当只有一名治愈患者时，医生会出现，而不是全部：

@physicians = Physician.includes(:patients) .where.not(patients: { id: nil }) .where(patients: { is_cured: true })

型号：

class Physician < ApplicationRecord
  has_many :patients
  has_many :recommendations, through: :patients
end

class Patient < ApplicationRecord
  belongs_to :physician
  belongs_to :recommendation
end

class Recommendation < ApplicationRecord
  has_many :patients
  has_many :physicians, through: :patients
end

感谢您提供的任何帮助！

Answer 1

# Fetches physicians who have at-least one uncured patient
phys_with_uncured_patients = Physician.joins(:patients).where(patients: { is_cured: false })

#Fetches physicians who have at-least one patient and all are cured.
Physician.joins(:patients).where.not(id: phys_with_uncured_patients)

Answer 2

physician_ids = Patient.where(is_cured: false).pluck(:physician_id)

Physician.joins(:patients).where.not(id: physician_ids)