Development & Testing

Sequelize ORM

Feature-rich promise-based ORM for Node.js supporting PostgreSQL, MySQL, MariaDB, SQLite, and MSSQL with model definitions and associations.

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Overview

Sequelize is a mature, promise-based ORM for Node.js that has been the go-to choice for SQL database access for over a decade. It supports PostgreSQL, MySQL, MariaDB, SQLite, and MSSQL with a consistent API across all dialects. AI agents can define models, set up associations, write queries, and manage migrations using Sequelize's comprehensive API.

Your AI agent can generate model definitions with validations, hooks, and custom instance/class methods. It can configure associations (hasOne, hasMany, belongsTo, belongsToMany), implement eager and lazy loading, and write complex queries using Sequelize's operator syntax. The migration system (sequelize-cli) provides a Rails-like workflow for evolving your database schema.

While newer ORMs like Prisma and Drizzle have gained popularity, Sequelize remains essential for maintaining existing projects and for teams that prefer the Active Record pattern. Your AI agent can help with upgrading between major versions, optimizing queries with raw SQL fallbacks, and configuring connection pooling for production deployments.

Who Is This For?

Node.js developers working with relational databases using the Active Record pattern
Teams maintaining legacy Sequelize codebases that need upgrades or new features
Backend engineers implementing complex model associations and validations
Developers needing cross-dialect database support within a single ORM

Installation

Setup for Claude Code

npm install sequelize pg pg-hstore
npm install -D sequelize-cli
npx sequelize-cli init
Claude Code generates models and migrations

Configuration

// models/User.ts
import { Model, DataTypes, Sequelize } from "sequelize";

const sequelize = new Sequelize(process.env.DATABASE_URL!);

class User extends Model {
  declare id: number;
  declare email: string;
  declare name: string;
}

User.init(
  {
    email: { type: DataTypes.STRING, allowNull: false, unique: true },
    name: { type: DataTypes.STRING, allowNull: false },
  },
  { sequelize, modelName: "User" },
);