I prefer use includes to connect my three tables. I have three model that I need to connect such as Register, Student, and Schedule. Here is my model Association

class Student < ApplicationRecord
    belongs_to :register
end

class Register < ApplicationRecord
    has_one :student

    belongs_to :schedule
end

class Schedule < ApplicationRecord
    belongs_to :course
    belongs_to :teacher

    has_many :days, :dependent => :destroy, :class_name => 'ScheduleDay'
    has_many :registers
end

Here is my controller

def index
        @students = Student.includes([register: :schedule])
        @students = @students.order 'students.created_at DESC'


        if params[:status_id] && params[:status_id].to_i > 0
            @students = @students.where 'students.status_id = ?', params[:status_id]
        end

        if params[:id] && params[:id].to_i > 0
            @students = @students.where 'cast(students.id as varchar) like (?)', "%#{params[:id]}%"
        end

        if params[:full_name] && params[:full_name].to_s.length > 0
            @students = @students.where 'lower(registers.name_in_indonesian || registers.name_in_chinese) like lower(?)', "%#{params[:full_name]}%"
        end

        if params[:course_id] && params[:course_id].to_i > 0
            @students = @students.where 'schedules.course_id = ?', params[:course_id]
        end

        @students = @students.paginate(page: params[:page], per_page: 30)
end

I got following error :

PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "schedules"
LINE 1: SELECT "students".* FROM "students" WHERE (schedules.course_...

I tried to debug by using rails console but end up with (Object doesn't support #inspect)