SQL vs NoSQL
 

 

Connect app to SQL database

npm install --save mysql2

  Connection setup

const mysql = require('mysql2');

// connection pool
// manage multiple connections (multiple queries) simultaneously.
const pool = mysql.createPool({
    host: 'localhost',
    user: 'root',
    database: 'node-complete',
    password:'Meiting5'
});

module.exports = pool.promise();

execute sql queries

db.execute('')

 

Sequelize

An object-relational mapping library

sequelize works with Promises

it does all the heavy lifting, all the SQL code behind the scenes for us and maps it into javascript objects with convenience methods which we can call to execute that behind the scenes SQL code so that we never have to write SQL code on our own.

 

npm install --save sequelize

 Connection setup

const Sequelize = require("sequelize");

const sequelize = new Sequelize("node-complete", "root", "Meiting5", {
  dialect: "mysql",
  host: "localhost"
});

module.exports = sequelize;

define model

const Product = sequelize.define('product',{
  id: {
    type:Sequelize.INTEGER,
    autoIncrement: true,
    allowNull: false,
    primaryKey: true
  },
  title: Sequelize.STRING,

  price:{
    type: Sequelize.DOUBLE,
    allowNull: false
  },
  imageUrl: {
    type: Sequelize.STRING,
    allowNull: false
  },
  description: {
    type: Sequelize.STRING,
    allowNull: false
  }
});

Create table

sequelize
  .sync()
  .then(result => {
    app.listen(3000);
  })
  .catch(err => {
    console.log(err);
  });

Insert Data & create a product

exports.postAddProduct = (req, res, next) => {
  const title = req.body.title;
  const imageUrl = req.body.imageUrl;
  const price = req.body.price;
  const description = req.body.description;
  Product.create({
    title: title,
    price: price,
    imageUrl: imageUrl,
    description: description
  })
    .then(result => {
      console.log("Created Product");
    })
    .catch(err => {
      console.log(err);
    });
};

Retrieving data and find products

Product.findAll()
   .then(products => {
      res.render("shop/index", {
        prods: products,
        pageTitle: "Shop",
        path: "/"
      });
    })
    .catch(err => console.log(err));

// Product.findAll({where: {id: prodId}})

Product.findByPk(prodId)
    .then((product) => {
      res.render("shop/product-detail", {
        product: product,
        pageTitle: product.title,
        path: "/products"
      });
    })
    .catch(err => console.log(err));

// create if not exist, overwrite if not exist
product.save();

delete

Product.findByPk(prodId)
    .then(product => {
      return product.destroy();
    })
    .then(result => {
      console.log("DESTROYED");
      res.redirect("/admin/products");
    })
    .catch(err => console.log(err));

 Associations

 

// delete user, all product associated to the user gone
Product.belongsTo(User,{constraints: true, onDelete: 'CASCADE'});
User.hasOne(Cart);

create new associated object

// pass data cannot be inferred by sequelize
req.user.createProduct({
    title: title,
    price: price,
    imageUrl: imageUrl,
    description: description
  })

.getProducts()