Migrations in NestJS - Mini Project: Build & Apply

Database Migrations with NestJS

📖 Scenario: You are building a simple NestJS application that manages a list of books. You need to set up database migrations to create and update the database schema safely over time.

🎯 Goal: Learn how to create and run migrations in a NestJS project using TypeORM to manage database schema changes step-by-step.

📋 What You'll Learn

Create an initial migration file to set up the books table

Add a configuration variable for the migration directory

Write a migration to add a new column to the books table

Run the migration and finalize the setup in the NestJS project

💡 Why This Matters

🌍 Real World

Database migrations help developers safely update database schemas as applications grow and change, avoiding data loss and keeping environments consistent.

💼 Career

Understanding migrations is essential for backend developers working with databases and frameworks like NestJS to maintain and evolve production databases.

1

Create Initial Migration File

Create a migration file named InitialBooksMigration that creates a table called books with columns id (primary key, auto-increment integer) and title (string). Use TypeORM migration syntax inside a class that extends MigrationInterface with up and down methods.

NestJS

import { MigrationInterface, QueryRunner, Table } from 'typeorm';

export class InitialBooksMigration implements MigrationInterface {
    public async up(queryRunner: QueryRunner): Promise {
        // Your code here
    }

    public async down(queryRunner: QueryRunner): Promise {
        // Your code here
    }
}

Need a hint?

Use queryRunner.createTable inside the up method to create the table. Use queryRunner.dropTable inside the down method to remove it.

2

Add Migration Directory Configuration

In your ormconfig.ts or equivalent TypeORM config file, add a configuration variable called migrationsDir and set it to 'src/migrations'. This will tell TypeORM where to find migration files.

NestJS

import { DataSourceOptions } from 'typeorm';

export const ormconfig: DataSourceOptions = {
    // Your code here
};

Need a hint?

Add migrationsDir: 'src/migrations' inside the exported config object.

3

Add Migration to Add Author Column

Create a new migration class named AddAuthorToBooksMigration that adds a new column called author of type varchar to the books table in the up method. In the down method, remove the author column.

NestJS

import { MigrationInterface, QueryRunner, TableColumn } from 'typeorm';

export class AddAuthorToBooksMigration implements MigrationInterface {
    public async up(queryRunner: QueryRunner): Promise {
        // Add author column here
    }

    public async down(queryRunner: QueryRunner): Promise {
        // Remove author column here
    }
}

Need a hint?

Use queryRunner.addColumn in up and queryRunner.dropColumn in down.

4

Run Migrations and Finalize Setup

In your NestJS main application file or migration script, import DataSource from typeorm, create a new DataSource instance using ormconfig, and call initialize() followed by runMigrations() to apply all pending migrations.

NestJS

const dataSource = new DataSource(ormconfig);

// Initialize and run migrations
// Your code here

Need a hint?

Call initialize() on the DataSource instance, then runMigrations() inside the then callback.