Search code examples
sqlruby-on-railsrubyruby-on-rails-4.2ruby-2.3

Rails: Query nil has_one association

I have two models: Patient and CodeStatus.

CodeStatus belongs_to Patient, and Patient has_one CodeStatus

I am trying to query all patients where patient.code_status is nil. I was surprised to find that Patient.where(code_status: nil) does not work throwing: column patients.patient_id does not exist

I have already found this (fairly old) answer, but I find it difficult to believe that the best way to query this is via a long string of raw SQL. I would think that rails would include this helper like they do for many other associations. Does anyone know of a less verbose solution to this? Thanks in advance.

Solution

  • The problem is, that

    patient.code_status

    is not a column, but a method, added by Rails when you say

    class Patient
  has_one :code_status
end

    Here is how you'd get all patients not associated with any code status:

    Patient.includes(:code_status).where(code_statuses: { id: nil })