Sequelize Fast-Track Roadmap — Phased Lessons

Goal: Learn Sequelize (Node.js ORM) quickly and deeply — one topic at a time, with theory + analogy + practical examples + exercises.

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Prerequisites (what you should already know)

• Basic JavaScript (ES6+), async/await
• Node.js and npm/yarn
• Basic SQL (SELECT, JOIN, INSERT, UPDATE) — not deep, just concepts
• Familiarity with Express.js (for building APIs) and React (for front-end integration)
• Git and terminal comfort

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PHASE 0 — Quick Setup (must-have)

• Choose a relational DB: Postgres (recommended), MySQL, MariaDB, SQLite (good for tests/dev).
• Packages you'll typically use:
  • sequelize (core)
  • sequelize-cli (optional but highly recommended for migrations/seeds)
  • dialect driver: pg + pg-hstore (Postgres), mysql2 (MySQL), mariadb (MariaDB), sqlite3 (SQLite), tedious (Microsoft SQL Server) and oracledb (Oracle Database)

Quick CLI starter commands (cheat-sheet):

npm init -y
npm install sequelize
npm install --save-dev sequelize-cli
# One of the following:
$ npm install --save pg pg-hstore # Postgres
$ npm install --save mysql2 # MySQL
$ npm install --save mariadb # MariaDB
$ npm install --save sqlite3 # SQLite
$ npm install --save tedious # Microsoft SQL Server
$ npm install --save oracledb # Oracle Database

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PHASE 1 — Fundamentals (minimum to be productive)

1. What is Sequelize & when to use it

   • Short: An ORM that maps JS objects to SQL tables and provides a high-level API.
   • Why it helps: Faster development, safer queries, cross-dialect portability.
   • Analogy: Sequelize is the translator between your JS code and the database.

2. Project setup & connection

   • Create Sequelize instance, environment config (dotenv), connection testing (sequelize.authenticate()), pool options.
   • Minimal code snippet included in lesson.

3. Models & DataTypes

   • sequelize.define() vs class Model extends Model + init().
   • DataTypes: STRING, INTEGER, BOOLEAN, DATE, JSON, TEXT, DECIMAL etc.
   • Field options: allowNull, defaultValue, unique, validate.

4. Migrations (why & how)

   • sequelize-cli setup, model:generate, migration up/down, running db:migrate.
   • Why migrations are preferable to sync({ force: true }) in production.

5. CRUD basics

   • create, findOne, findAll, findByPk, update, destroy.
   • findOrCreate, increment, decrement.

6. Associations (basic)

   • hasOne, belongsTo, hasMany, belongsToMany (through table).
   • FK ownership, onDelete/onUpdate behaviors.

7. Querying & Operators

   • where clause, Op operators (Op.gt, Op.like, Op.in, Op.or), attributes, order, limit, offset.

8. Hooks & Validations

   • Lifecycle hooks: beforeCreate, afterUpdate, etc.
   • Built-in validations and custom validators.

9. Transactions (essential)

   • Managed vs unmanaged transactions, passing { transaction: t }, rollback behavior.

10. Integrating with Express (simple REST)

• Pattern for controllers, error handling, request → DB flow.

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PHASE 2 — Intermediate (deeper practical skills)

1. Advanced Associations

   • Many-to-many through models with extra fields, aliasing (as), through options.

2. Eager loading patterns

   • Nested include, selecting attributes per association, required vs optional join, separate: true for large collections.

3. Scopes & Query Helpers

   • defaultScope, named scopes, reusable query patterns.

4. Model options & indexes

   • paranoid (soft delete), timestamps, underscored, schema support, indexes for performance.

5. Bulk operations & performance

   • bulkCreate, bulkUpdate (via update with where), upsert, RETURNING behavior.

6. Raw queries & SQL security

   • sequelize.query() with replacements/binds, avoiding SQL injection, when to use raw SQL.

7. Pagination (offset & cursor-based)

   • Implementing efficient pagination and considerations for large datasets.

8. Connection pooling & config tuning

   • Pool params, reconnect logic, logging control.

9. Testing models

   • In-memory SQLite for unit tests, factories, seeding test data, mocking.

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PHASE 3 — Advanced

These are advanced topics you can learn after the intermediate set.

1. Polymorphic & Self-referential associations

   • Implementing tagging systems, comment threading, recursive relations.

2. Multi-tenant patterns

   • Row-based vs schema-based tenancy, pros/cons, migration strategies.

3. Zero-downtime migrations & production workflows

   • Adding columns safely, backfilling data, rollouts.

4. Complex query optimization

   • Explain plans, index strategies, denormalization trade-offs.

5. Sequelize + GraphQL + DataLoader

   • N+1 problem, batching resolver patterns, dataloader integration.

6. TypeScript + Sequelize

   • Typings, sequelize-typescript or manual typing patterns, pros/cons.

7. Custom data types, getters/setters, virtual fields

   • Virtual attributes, JSON columns, custom casting.

8. Contributing to Sequelize / reading source

   • How to navigate the library codebase if you want to contribute or debug.

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Capstone Projects (pick one to build end-to-end)

• Blog + Comments + Tags: Users, Posts, Comments, Tags (many-to-many). Full REST API + React front-end. Auth, pagination, search.
• E-commerce-ish: Products, Categories, Orders, OrderItems, Inventory, Payments (mock). Multi-table transactions for checkout.
• Job board: Jobs, Companies, Applicants, resume upload (file handling), search filters.

Each capstone will be split into tasks and lessons (DB design, models, migrations, APIs, frontend integration, testing, deployment).

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Quick Best Practices (summary)

• Use migrations in all non-trivial projects; avoid sync({ force: true }) in prod.
• Keep models thin: validation + relations. Put business logic in services.
• Always use transactions when multiple related writes happen.
• Watch SQL logs while developing to understand generated queries.
• Use parameterized queries / replacements for raw SQL.
• Add indexes based on query patterns, not prematurely.

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How I will teach each topic (my lesson format)

1. One-paragraph explanation + real-world analogy
2. Minimal code example with comments (ready to run)
3. Step-by-step walkthrough of the code
4. Common pitfalls & debugging tips

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Download Roadmap

• Click here to download roadmap in Word format.
• Click here to download roadmap in PDF format.

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👤 Author

Darsh Parikh

• 💼 GitHub: @DarshParikh25
• 🔗 LinkedIn: darshparikh
• 📫 Email: darshparikh00@gmail.com

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Made with ❤️ by Darsh Parikh