Database schema and Stock model for a StackOverflow question. http://stackoverflow.com/questions/27209916/rails-unintentionally-inserts-default-values-into-database

schema.rb

# encoding: UTF-8
# This file is auto-generated from the current state of the database. Instead
# of editing this file, please use the migrations feature of Active Record to
# incrementally modify your database, and then regenerate this schema definition.
#
# Note that this schema.rb definition is the authoritative source for your
# database schema. If you need to create the application database on another
# system, you should be using db:schema:load, not running all the migrations
# from scratch. The latter is a flawed and unsustainable approach (the more migrations
# you'll amass, the slower it'll run and the greater likelihood for issues).
#
# It's strongly recommended that you check this file into your version control system.

ActiveRecord::Schema.define(version: 20141101001603) do

  create_table "exchanges", force: true do |t|
    t.string "name"
    t.string "exchange_id", default: "", null: false
  end

  add_index "exchanges", ["exchange_id"], name: "index_exchanges_on_exchange_id", unique: true

  create_table "exchanges_stocks", id: false, force: true do |t|
    t.string "exchange_id"
    t.string "symbol"
  end

  create_table "stocks", id: false, force: true do |t|
    t.string "symbol",         default: "", null: false
    t.string "name"
    t.string "stock_exchange"
    t.string "color"
  end

  add_index "stocks", ["symbol"], name: "index_stocks_on_symbol"

  create_table "stocks_users", id: false, force: true do |t|
    t.string  "symbol"
    t.integer "user_id"
  end

  create_table "users", force: true do |t|
    t.string   "email",                  default: "", null: false
    t.string   "encrypted_password",     default: "", null: false
    t.string   "reset_password_token"
    t.datetime "reset_password_sent_at"
    t.datetime "remember_created_at"
    t.integer  "sign_in_count",          default: 0,  null: false
    t.datetime "current_sign_in_at"
    t.datetime "last_sign_in_at"
    t.string   "current_sign_in_ip"
    t.string   "last_sign_in_ip"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  add_index "users", ["email"], name: "index_users_on_email", unique: true
  add_index "users", ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true

end

stock.rb

class Stock < ActiveRecord::Base
  self.primary_key = 'symbol'
  attr_accessor :symbol, :name, :color

  belongs_to :user
  belongs_to :exchange

  has_one :symbol
  has_one :name
  has_one :color

  def to_param
    symbol.parameterize
  end

  def self.not_exists?(symbol)
    self.find(symbol)
    false
  rescue
    true
  end
end