Adding and removing columns in Ruby on Rails - Mini Project: Build & Apply

Adding and Removing Columns in Rails

📖 Scenario: You are working on a Rails app that manages a list of books. You need to update the database to add a new column for the book's genre and later remove the published_year column.

🎯 Goal: Create a Rails migration to add a genre column of type string to the books table, then create another migration to remove the published_year column from the same table.

📋 What You'll Learn

Create a migration file to add a genre column of type string to the books table

Create a migration file to remove the published_year column from the books table

Use the correct Rails migration methods add_column and remove_column

Name the migration classes correctly following Rails conventions

💡 Why This Matters

🌍 Real World

Adding and removing columns is a common task when evolving a Rails app's database to support new features or remove outdated data.

💼 Career

Rails developers frequently write migrations to update database schemas safely and maintain data integrity during app development.

1

Create migration to add genre column

Create a migration class called AddGenreToBooks that inherits from ActiveRecord::Migration[7.0]. Inside the change method, add a genre column of type string to the books table using add_column.

Ruby on Rails

class AddGenreToBooks < ActiveRecord::Migration[7.0]
  def change
    # Your code here
  end
end

Need a hint?

Use add_column :books, :genre, :string inside the change method.

2

Create migration to remove published_year column

Create a migration class called RemovePublishedYearFromBooks that inherits from ActiveRecord::Migration[7.0]. Inside the change method, remove the published_year column from the books table using remove_column.

Ruby on Rails

class AddGenreToBooks < ActiveRecord::Migration[7.0]
  def change
    add_column :books, :genre, :string
  end
end

class RemovePublishedYearFromBooks < ActiveRecord::Migration[7.0]
  def change
    # Your code here
  end
end

Need a hint?

Use remove_column :books, :published_year inside the change method.

3

Add migration timestamps

Add the timestamps method call inside the change method of the AddGenreToBooks migration class to track when records are created or updated.

Ruby on Rails

class AddGenreToBooks < ActiveRecord::Migration[7.0]
  def change
    add_column :books, :genre, :string
    # Your code here
  end
end

class RemovePublishedYearFromBooks < ActiveRecord::Migration[7.0]
  def change
    remove_column :books, :published_year
  end
end

Need a hint?

Call timestamps inside the change method to add created_at and updated_at columns.

4

Add reversible migration for removing column

Modify the change method in the RemovePublishedYearFromBooks migration class to use reversible with remove_column and add_column so the migration can be rolled back safely. Remove the timestamps call from the AddGenreToBooks migration.

Ruby on Rails

class AddGenreToBooks < ActiveRecord::Migration[7.0]
  def change
    add_column :books, :genre, :string
    # Remove timestamps here
  end
end

class RemovePublishedYearFromBooks < ActiveRecord::Migration[7.0]
  def change
    reversible do |dir|
      # Your code here
    end
  end
end

Need a hint?

Use reversible do |dir| with dir.up and dir.down blocks to safely remove and add back the column.

Remove the timestamps call from the first migration.