Create the config file called .sequelizerc in the root directory, should contain the following code:

// .sequelizerc
const path = require('path');

module.exports = {
  config: path.resolve('config', 'database.json'),
  'models-path': path.resolve('db', 'models'),
  'migrations-path': path.resolve('db', 'migrations')
};

• Use config/database.json file for config settings
• Use db/models as models folder
• Use db/migrations as migrations folder

$ node_modules/.bin/sequelize init

This will create an empty project by creating the corresponding folders specified in the config file.

Dependencies installed locally will use the command pattern node_modules/.bin/sequelize instead of using sequelize directly

The index.js file lives in models folder has the following code:

// db/models/index.js
...
const env = process.env.NODE_ENV || 'development';
const config = require(__dirname + '/../../config/database.json')[env];

...
if (config.use_env_variable) {
  sequelize = new Sequelize(process.env[config.use_env_variable], config);
} else {
  sequelize = new Sequelize(config.database, config.username, config.password, config);
}
...

The config.use_env_variable is what needs to be setting its value with the environment variables. Also note that the config variable is pointed to database.json file in config folder, will update that file as well later.

• Install dotenv

  $ yarn add dotenv

• Require dotenv file at the top of index.js

  // db/models/index.js
  require('dotenv').config();

• Create .env file in the root directory, should contain the following code

  // .env
  DATABASE_URL=postgres://username@localhost:5432/database_name

  This will contain all node environment variables, for now it only contains the DB endpoint.

• Replace development section with the following code in database.json file:

   // config/database.json
  "development": {
    "use_env_variable": "DATABASE_URL"
  },

With all that being set, config.use_env_variable will now have the value of the DB endpoint on development environment.

The goal is to have each Todo with multiple TodoItems.

• Create Todo model with the following command:

  $ node_modules/.bin/sequelize model:create --name Todo --attributes title:string

  • --name refers to the name of the model
  • --attribute refers to the attributes the model should have

  This will generate a todo.js file in the models folder and a corresponding migration file in the migration folder.

• Create TodoItems with the following command:

  $ node_modules/.bin/sequelize model:create --name TodoItem --attributes description:string

• Create relationship between Todo and TodoItem

  Add the following code in todo.js file:

  // db/models/todo.js
  ...
  Todo.associate = function(models) {
    // associations can be defined here
    Todo.hasMany(models.TodoItem, {
      foreignKey: 'todoId'
    });
  };
  ...

  The Todo.hasMany sets the relationship as one-to-many. While the foreignKey: 'todoId' means that todoId is going to be the foreign key column in TodoItem. Let's add that:

  // db/models/todoitem.js
  ...
  TodoItem.associate = function(models) {
    // associations can be defined here
    TodoItem.belongsTo(models.Todo, {
      foreignKey: 'todoId',
      onDelete: 'CASCADE'
    });
  };
  ...

  The TodoItem.belongsTo sets each TodoItem to be linked to one Todo. The onDelete: 'CASCADE' means if a Todo is deleted then the associated TodoItem should also be deleted.

• Modify the migration script for TodoItem to include a todoId field

  Add the following code to the file:

  ...
  todoId: {
    type: Sequelize.INTEGER,
    onDelete: 'CASCADE',
    references: {
      model: 'Todos',
      key: 'id',
      as: 'todoId',
    },
  },
  ...

  • model tells which model this ForeignKey refers to

$ node_modules/.bin/sequelize db:migrate

The database should now have the tables created with the relationship being set and defined.

Install Postgres.app and follow setup instructions.

Install the postgres CLI tools.

Open up a new terminal window to ensure your changes have been saved.

Verify that it worked correctly. The psql should point to the path containing the Postgres.app directory.

$ which psql
/Applications/Postgres.app/Contents/Versions/latest/bin/psql