Get parent objects without active childs - sql

Question

I've two models, Doctor and DoctorClinic where a doctor has_many clinics.
doctor.rb:
has_many :clinics, class_name: 'DoctorClinic', dependent: :destroy
doctor_clinic.rb
belongs_to :doctor
DoctorClinic have doctor_id and a boolean active field.
What I want:
I want to get all doctors which does not have any active (active field is true) clinics. If a doctor have two clinics, out of which one is active and other is inactive then doctor should not be selected.
Doctor record will be selected if,
there's no clinics at all
if there's any clinic but all are inactive, i.e. all have active false.
Doctor will not be selected if,
there's any active clinics.
What I've tried so far:
Try 1:
scope :incomplete_doctors, -> { includes(:clinics)
.where("( doctor_clinics.id IS NULL ) OR
( doctor_clinics.id IS NOT NULL AND
doctor_clinics.active=?)", false )
}
Try 2:
scope :incomplete_doctors, -> { where("id NOT IN (?)", self.includes(:clinics)
.where("( doctor_clinics.doctor_id IS NULL ) OR
( doctor_clinics.doctor_id IS NOT NULL AND
doctor_clinics.active=?)", false )
.select(:id))
}
Try 3:
SELECT "doctors".* FROM "doctors"
LEFT OUTER JOIN "doctor_clinics" ON "doctor_clinics"."doctor_id" = "doctors"."id"
WHERE ( ( doctor_clinics.id IS NULL ) OR
( doctor_clinics.id IS NOT NULL AND
doctor_clinics.active='f'))
GROUP BY doctors.id
HAVING 'true' <> ANY(array_agg(DISTINCT doctor_clinics.active::TEXT));
Success:
I'm able to achieve desired output using following method, but I want to achieve this using a SQL query.
def active_clinics
clinics.active_clinics # active_clinics is a scope in Clinic model while give all active clinics
end
def self.incomplete_doctors
(Doctor.all.map { |d| d unless d.active_clinics.present? }).compact
end

Answer 1

Something like this should do the trick in pure SQL
SELECT *
FROM doctors
WHERE NOT EXISTS (
SELECT 1
FROM doctor_clinics
WHERE
doctor_clinics.doctor_id = doctors.id
AND doctor_clinics.active = true
)
You should be able to use it with find_by_sql:
Doctor.find_by_sql(SQL)
Have no Rails 3 project to actually test it;-)