Running and rolling back migrations in Ruby on Rails

Introduction

Migrations help you change your database step-by-step. Running migrations applies changes. Rolling back undoes them if needed.

When you add a new table or column to your database

When you fix a mistake in a previous database change

When you want to test changes without permanently applying them

When you need to reset your database to a previous state

When collaborating with others and syncing database changes

Syntax

Ruby on Rails

rails db:migrate
rails db:rollback STEP=n

rails db:migrate runs all pending migrations in order.

rails db:rollback undoes the last migration by default. Use STEP=n to undo multiple steps.

Examples

This runs all new migrations that have not been applied yet.

Ruby on Rails

rails db:migrate

This rolls back the last migration that was run.

Ruby on Rails

rails db:rollback

This rolls back the last 3 migrations in reverse order.

Ruby on Rails

rails db:rollback STEP=3

Sample Program

First, we run all pending migrations to update the database. Then, we undo the last migration. Finally, we undo the last two migrations to go back further.

Ruby on Rails

# Run migrations
rails db:migrate

# Rollback last migration
rails db:rollback

# Rollback last 2 migrations
rails db:rollback STEP=2

Important Notes

Always check your migration files before running or rolling back to avoid data loss.

Rolling back migrations only affects the database schema, not your application code.

You can use rails db:migrate:status to see which migrations have run.

Summary

Running migrations applies database changes step-by-step.

Rolling back undoes migrations to fix or test changes.

Use STEP=n with rollback to undo multiple migrations at once.