SequelizeJS for Dummies

21.04.2021

Daniel Mocan

Content

What are ORM's?

Why SequelizeJS?

Setup

Models

Queries

Migrations

 

Demo

Q&A

What are ORM's

Object-Relational Mapping is a technique that lets you query and manipulates data from a database using an object-oriented paradigm. ORM loves objects as much as developers, and is available for any programming language of your choosing.

What are ORM's

Prons

easy to switch the database

Cons

protection agains SQL injection

same programming language

more advance features

complex SQL

initial setup

SQL expert

Why SequelizeJS

Probably the most used JS ORM

Multiple databases: Postgres, MySQL, MariaDB, SQLite and Microsoft SQL Server

around 4 million downloads pe month

actively being developed 

preaty easy to use

lots of feature / options / configurations

Setup

# Core Packeage 
npm install --save sequelize

# Dependecies for the type of database you want to use

npm install --save pg pg-hstore # Postgres
npm install --save mysql2
npm install --save mariadb
npm install --save sqlite3
npm install --save tedious # Microsoft SQL Server

Setup

const { Sequelize } = require('sequelize');

const sequelize = new Sequelize({
  dialect: 'sqlite',
  storage: 'storage/data.sqlite',
  logging: console.log,
});

(async () => {
    try {
        await sequelize.authenticate();
        await sequelize.sync();
        console.log('Connection has been established successfully.');
    } catch (error) {
        console.error('Unable to connect to the database:', error);
    }
})();

module.exports = sequelize;

Models

const { DataTypes, Model } = require('sequelize');
const sequelize = require('./sequelize');

class Post extends Model {}

Post.init({
    id: {
        type: DataTypes.INTEGER,
        allowNull: false,
        primaryKey: true,
        autoIncrement: true,
    },
    title: {
        type: DataTypes.STRING,
        allowNull: false
    },
}, {
  sequelize, // We need to pass the connection instance
  modelName: 'Post' // We need to choose the model name
});

module.exports = Post;

Models

// creating an instance of a model
const firstPost = await PostModel.build({ 
  	title: "What is Binery?", 
  	content: "Binery is a invented romania word. If is a cominations for Bine (good) and Vineri (Friday). Resulting word Binery express the feeling its good its Friday"
});

await firstPost.save();

// another option to create an instance of a model
const post = await PostModel.create({
    title: "Third Post", 
    content: "long content"
});

Queries

const { Op } = require('sequelize');

// Finding a single post
const post = await Post.findOne({ id });

// Finding more mosts and count them
const { count, rows } = await Post.findAndCountAll({
  where: {
    title: {
      [Op.like]: 'foo%'
    }
  },
  offset: 10,
  limit: 2
});

Queries

// Sequelize setup file
const sequelize = require('./sequelize');

//Simple select using RawQuery
const getPostsSQL = 'SELECT * FROM Posts';
const [results, metadata] = await sequelize.query(getPostsSQL);

// Even simpler so you don't have to get use the results
const { QueryTypes } = require('sequelize');
const posts = await sequelize.query(
  'SELECT * FROM Posts', 
  { type: QueryTypes.SELECT }
);

Migrations

npm install --save-dev sequelize-cli

// init will create a few folders like config, migrations, models, etc.
npx sequelize-cli init

Migrations

// Our first migration file
module.exports = {
  up: async (queryInterface, Sequelize) => {
    await queryInterface.createTable('Posts-migrations', {
      id: {
        allowNull: false,
        autoIncrement: true,
        primaryKey: true,
        type: Sequelize.INTEGER
      },
      title: {
        type: Sequelize.STRING
      },
      content: {
        type: Sequelize.STRING
      },
      createdAt: {
        allowNull: false,
        type: Sequelize.DATE
      },
      updatedAt: {
        allowNull: false,
        type: Sequelize.DATE
      }
    });
  },
  down: async (queryInterface, Sequelize) => {
    await queryInterface.dropTable('Posts-migrations');
  }
};

Demo

Thank you

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