PatientVisitDetailsController＃auto_build中的ActiveRecord :: StatementInvalid

Question

我有模特

class PatientVisitDetail < ActiveRecord::Base
  belongs_to :procedure_code
  scope :billable, -> { includes(:procedure_code).where('procedure_codes.type_code IN (6,7)')}
end

并且

class ProcedureCode < ActiveRecord::Base
  has_many :patient_visit_details, :dependent => :destroy
end

当我通过查询搜索记录时，如

patient_visit_details.includes(:procedure_code).where("procedure_codes.type_code IN (6,7)")

然后出现以下错误

Mysql2::Error: Unknown column 'procedure_codes.type_code' in 'where clause': SELECT COUNT(*) FROM `patient_visit_details` WHERE `patient_visit_details`.`deleted_at` IS NULL AND (patient_visit_id > 0) AND `patient_visit_details`.`patient_visit_id` = 6 AND (procedure_codes.type_code IN (6,7))

type_code存在于数据库中，但仍然是未知列。