Rails -- ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column:

Question

Having major Rails issues currently. I'm creating a School-Dashboard app that takes an xref table called Enrollments that relates Courses and Students.

Any time I try to update a grade for an Enrollment, I constantly get this line

ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: UPDATE
"enrollments" SET "grade" = ?, "updated_at" = ? WHERE "enrollments"."" IS NULL

This line does not appear when I update attributes for Courses or Students. Only for the :grade attribute in Enrollment. For some reason, it isn't being read properly, even though it is a legitimate attribute in my db for Enrollment (check out my schema).

I do all of my preliminary work in the rails sandbox. Using ruby 2.1.1, Rails 4.1.0.rc1

I'd really love some help here.

Here are my corresponding models

class Student < ActiveRecord::Base
   has_many :enrollments
   has_many :courses, through: :enrollments
end

class Course < ActiveRecord::Base
   has_many :enrollments
   has_many :students, through: :enrollments
end

class Enrollment < ActiveRecord::Base
    belongs_to :student
    belongs_to :course
end

The controllers:

Students

class StudentsController < ApplicationController
   def index
      @students = Student.all
   end

   def new
      @student = Student.new
   end

   def show
   end

   def update
      @student.update_attributes(student_params) ? redirect_to @student : render 'edit'
   end

   def create
      @student = Student.new(student_params)
      @student.save ? redirect_to @student : render 'new' 
   end

   def destroy
   end

   def edit
   end

   private
   def student_params
      params.require(:student).permit(:first_name, :last_name, :student_number, :email)
  end
 end

Courses

class CoursesController < ApplicationController
   def index
     @courses = Course.all
   end

   def new
     @course = Course.new
   end

   def show
   end

   def update
     @course.update_attributes(course_params) ? redirect_to @course : render 'edit'
   end

   def create
     @course = Course.new(course_params)
     @course.save ? redirect_to @course : render 'new'
   end

   def destroy
   end

   def edit
     # code here
   end

   private
   def course_params
     params.require(:course).permit(:course_name, :course_number)
   end
 end

Enrollments

class EnrollmentsController < ApplicationController
   attr_accessor :course_id, :student_id, :grade
   def index
     @enrollments = Enrollment.all
   end

   def new
     @enrollment = Enrollment.new
   end

   def create
     @enrollment = Enrollment.new(enrollment_params)
     @enrollment.save ? redirect_to @enrollment : render 'new'
   end

   def update
     @enrollment.update_attributes(enrollment_params) ? redirect_to @enrollment : render  'edit'
   end

   def show
   end

   def destroy
     @enrollment.destroy
   end

   def edit
     # code here
   end

   private
   def enrollment_params
     params.require(:enrollment).permit(:course_id, :student_id, :grade)
   end
 end

And finally my schema.rb

 ActiveRecord::Schema.define(version: 20140417152720) do

   create_table "courses", force: true do |t|
     t.string   "course_name"
     t.integer  "course_number"
     t.datetime "created_at"
     t.datetime "updated_at"
   end

   create_table "enrollments", id: false, force: true do |t|
     t.integer  "course_id",                          null: false
     t.integer  "student_id",                         null: false
     t.decimal  "grade",      precision: 5, scale: 2
     t.datetime "created_at"
     t.datetime "updated_at"
   end

   # noinspection RailsParamDefResolve
   add_index "enrollments", ["course_id", "student_id"], name: "index_enrollments_on_course_id_and_student_id"
   # noinspection RailsParamDefResolve
   add_index "enrollments", ["student_id", "course_id"], name: "index_enrollments_on_student_id_and_course_id"

   create_table "students", force: true do |t|
     t.string   "first_name"
     t.string   "last_name"
     t.string   "email"
     t.integer  "student_number"
     t.datetime "created_at"
     t.datetime "updated_at"
   end
 end

Answer 1

Looks like I figured it out on my own!

So here's a bit of rails convention that needs to be addressed. The problem was with my database setup for 'Enrollments'. When I run the command
rails g migration CreateJoinTableEnrollments course student
Rails does too much work for me in my migration file (except for the table name and grade, I added that)

class CreateJoinTableEnrollments < ActiveRecord::Migration
  def change
     create_join_table :courses, :students, table_name: :enrollments, id: false, force: true do |t|
       t.index [:course_id, :student_id], null: false
       t.index [:student_id, :course_id], null :false
       t.decimal :grade, precision: 5, scale: 2
       t.timestamps
    end
   end
 end

In reality, I didn't need any of that. In order to manipulate specific data in a row for Enrollments, there has to be an identifier for that row. With id: false, force: true that option got nullified. I also simplified things with the indexing. I just created regular old columns instead. Now my migration file looks like this.

class CreateJoinTableEnrollments < ActiveRecord::Migration
   def change
      create_table :enrollments do |t|
         t.integer :course_id, null: false
         t.integer :student_id, null: false
         t.decimal :grade, precision: 5, scale: 2

         t.timestamps
      end
    end
  end

And with that, no issues! I've just been breaking my head over that for the past 2 days. Hope this helps anyone else who has this issue.