model.js

var Sequelize = require('sequelize');

var sequelize = new Sequelize('userpets', 'dbuser', 'dbpassword', {
  host: 'localhost', //mysql host name
  port: 3306 //default mysql port
});

var User = sequelize.define(
  'User',
  {
    firstName: { type: Sequelize.STRING },
    lastName: { type: Sequelize.STRING },
    password: { type: Sequelize.STRING },
    numberOfPets: { type: Sequelize.INTEGER }
  }
);

var Pet = sequelize.define(
  'Pet',
  {
    name: { type: Sequelize.STRING },
    type: { type: Sequelize.STRING }
  }
);

Pet.belongsTo(User, { as: 'Owner' });
User.hasMany(Pet, { as: 'Pets' });

var chainer = new Sequelize.Utils.QueryChainer;
chainer.add(User.sync());
chainer.add(Pet.sync());

chainer
  .run()
  .on('success', function () {
    addUserAndAPet();
  })
  .on('error', function (e) {
    console.log('Something went wrong!', e)
  });

function addUserAndAPet () {

  var user, dog, chainer;

  user = User.build({
    firstName: 'foo',
    lastName: 'bar',
    password: 'asdfasdf',
    numberOfPets: 0
  });

  dog = Pet.build({
    name: 'bono',
    type: 'DOG'
  });

  var chainer = new Sequelize.Utils.QueryChainer;

  chainer.add(user.save());
  chainer.add(dog.save());
  chainer
    .run()
    .on('success', function () {
      assignOwner(user, dog);
    })
    .on('error', function () {
      console.log('Could not add user or pet');
    });
}

function assignOwner (user, pet) {

  var chainer = new Sequelize.Utils.QueryChainer;

  chainer.add(pet.setOwner(user));
  chainer.add(user.updateAttributes({
    numberOfPets: user.numberOfPets + 1
  }));

  chainer
    .runSerially()
    .on('success', function () {
      console.log(user.firstName + ' is the owner of ' + pet.name);
    })
    .on('error', function () {
      console.log('Could not assign owner :(');
    });
}

exports.User = User;