Introduction to Sequelize
Sequealize follows the promise-based Node.js ORM for different servers like – Postgres, MySQL, MariaDB, SQLite, and Microsoft SQL Server.
Following are some of the main features of NodeJS sequelize −
Transaction Support
Relations
Eager and Lazy Loading
Read Replication and more...
Connecting to MySQL using Sequelize
We need to establish a connection between MySQL and Node.js using Sequelize.
After creating a successful connection with sequelize, we would require the following three files for configuration. Please carefully create the following files in their respective folders only.
SequelizeDemo > application.js
This will be our root file which will hold the actual logic.
SequelizeDemo>utils>database.js
This will hold all the connection details to MySQL.
SequelizeDemo>models>user.js
This will contain the required model information.
Example
Configure Database.js
const Sequelize = require('sequelize') const sequelize = new Sequelize( 'YOUR_DB_NAME', // TutorialsPoint 'YOUR_DB_USER_NAME', // root 'YOUR_DB_PASSWORD', //root{ dialect: 'mysql', host: 'localhost' } ); module.exports = sequelize
Please make all the inputs for connecting with your database.
Configure User.js
Use this file to define the mappings between a model and a table.
const Sequelize = require('sequelize') const sequelize = require('../utils/database') const User = sequelize.define('user', { // Name of Column #1 and its properties defined: id user_id:{ // Integer Datatype type:Sequelize.INTEGER, // Increment the value automatically autoIncrement:true, // user_id can not be null. allowNull:false, // To uniquely identify user primaryKey:true }, // Name of Column #2: name name: { type: Sequelize.STRING, allowNull:false }, // Name of Column #3: email email: { type: Sequelize.STRING, allowNull:false }, // Column: Timestamps createdAt: Sequelize.DATE, updatedAt: Sequelize.DATE, }) module.exports = User
Configure app.js
To create a model, we can use any one of the two methods −
sync() Method − Only create model if exists. If the model exists, it will not overwrite the model.
sync({force: true}) Method − Will create a new model if the model does not exist, however, if the model exists, it will overwrite the existing model.
// Importing the database model const sequelize = require('./database') // Importing the user model const User = require('./user') // Creating all the tables defined in user sequelize.sync() // You can change the user.js file // And run this code to check if it overwrites the existing code. sequelize.sync({force:true)
Output
On running the above program, you will get the following Output -
C:\\Users\SequelizeDemo>> node app.js Executing (default): CREATE TABLE IF NOT EXISTS `users` (`user_id` INTEGER NOT NULL auto_increment , `name` VARCHAR(255) NOT NULL, `email` VARCHAR(255) NOT NULL, `createdAt` DATETIME, `updatedAt` DATETIME, PRIMARY KEY (`user_id`)) ENGINE=InnoDB; Executing (default): SHOW INDEX FROM `users`
Now, you can check your database. The above table would have been created.