Ruby - Query another table in a model definition

I want to query another table in a model definition. For instance, I have a table called miq_user_roles and I want to query and retrievesettings column value.

I tried adding the following

has_many   :miq_user_roles

but when I try the where condition where(:settings => nil)

I get the error service_template doesn't have settings column. How can I query miq_user_roles for settings instead of service_template

service_template has a column called miq_group_id and its the id of miq_user_rolestable.

Following is the actual model definition where I want to include miq_user_roles table.

class ServiceTemplate < ApplicationRecord
  include SupportsFeatureMixin

  DEFAULT_PROCESS_DELAY_BETWEEN_GROUPS = 120

  GENERIC_ITEM_SUBTYPES = {
    "custom"          => N_("Custom"),
    "vm"              => N_("Virtual Machine"),
    "playbook"        => N_("Playbook"),
    "hosted_database" => N_("Hosted Database"),
    "load_balancer"   => N_("Load Balancer"),
    "storage"         => N_("Storage")
  }.freeze

  SERVICE_TYPE_ATOMIC    = 'atomic'.freeze
  SERVICE_TYPE_COMPOSITE = 'composite'.freeze

  RESOURCE_ACTION_UPDATE_ATTRS = [:dialog,
                                  :dialog_id,
                                  :fqname,
                                  :configuration_template,
                                  :configuration_template_id,
                                  :configuration_template_type].freeze

  include CustomActionsMixin
  include ServiceMixin
  include OwnershipMixin
  include NewWithTypeStiMixin
  include TenancyMixin
  include ArchivedMixin
  include CiFeatureMixin
  include_concern 'Filter'
  include_concern 'Copy'


  validates :name, :presence => true
  belongs_to :tenant

  has_many   :service_templates, :through => :service_resources, :source => :resource, :source_type => 'ServiceTemplate'
  has_many   :services


  has_many :service_template_tenants, :dependent => :destroy
  has_many :additional_tenants, :through => :service_template_tenants, :source => :tenant, :dependent => :destroy

  has_one :picture, :dependent => :destroy, :as => :resource, :autosave => true

  belongs_to :service_template_catalog
  belongs_to :zone
  belongs_to :currency, :inverse_of => false

  has_many   :dialogs, -> { distinct }, :through => :resource_actions
  has_many   :miq_schedules, :as => :resource, :dependent => :destroy

  has_many   :miq_requests, :as => :source, :dependent => :nullify
  has_many   :active_requests, -> { where(:request_state => MiqRequest::ACTIVE_STATES) }, :as => :source, :class_name => "MiqRequest"

  virtual_column   :type_display,                 :type => :string
  virtual_column   :template_valid,               :type => :boolean
  virtual_column   :template_valid_error_message, :type => :string
  virtual_column   :archived,                     :type => :boolean
  virtual_column   :active,                       :type => :boolean

  default_value_for :internal, false
  default_value_for :service_type, SERVICE_TYPE_ATOMIC
  default_value_for(:generic_subtype) { |st| 'custom' if st.prov_type == 'generic' }

  virtual_has_one :config_info, :class_name => "Hash"

  scope :with_service_template_catalog_id,          ->(cat_id) { where(:service_template_catalog_id => cat_id) }
  scope :without_service_template_catalog_id,       ->         { where(:service_template_catalog_id => nil) }
  scope :with_existent_service_template_catalog_id, ->         { where.not(:service_template_catalog_id => nil) }
  scope :displayed,                                 ->         { where(:display => true) }
  scope :public_service_templates,                  ->         { where(:display => true) }


  supports :order do
    unsupported_reason_add(:order, 'Service template does not belong to a service catalog') unless service_template_catalog
    unsupported_reason_add(:order, 'Service template is not configured to be displayed') unless display
  end
  alias orderable?     supports_order?
  alias validate_order supports_order?


  def self.with_tenant(tenant_id)
    tenant = Tenant.find(tenant_id)
    where(:tenant_id => tenant.ancestor_ids + [tenant_id])\
  end