Handling Complex Relationships with Sequelize in Node.js

Managing complex relationships in relational databases can be challenging, especially when dealing with large datasets and intricate data models. Sequelize, a popular Node.js ORM (Object-Relational Mapping) library, simplifies this process by providing an intuitive API for defining and querying relationships in databases like MySQL and PostgreSQL.

In this article, we’ll dive into how Sequelize handles one-to-one, one-to-many, and many-to-many relationships, along with practical examples and advanced features like eager loading and transactions.

Setting Up Sequelize with MySQL/PostgreSQL

First, let’s set up a Sequelize project connected to either MySQL or PostgreSQL.

Installation

Run the following command to install Sequelize and the appropriate database driver:

npm install sequelize mysql2 # for MySQL
# OR
npm install sequelize pg pg-hstore # for PostgreSQL

Initialization

Initialize Sequelize and define the connection:

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

// MySQL example
const sequelize = new Sequelize('database_name', 'username', 'password', {
    host: 'localhost',
    dialect: 'mysql',
})…