How to Use "rails g migration add column" in Rails

To add a column using the “rails g migration” command, you first need to open a terminal window and navigate to the root directory of your Rails project. From there, you can run the following command:

rails g migration add_column_name_to_table_name column_name:data_type

Replace “column_name” with the name of the column you want to add, “data_type” with the type of data that the column will hold (e.g., string, integer, boolean), and “table_name” with the name of the table in the database to which you want to add the column.

Example Command

For example, if you wanted to add a column called “email” to a table called “users” that holds string data, you would run the following command:

rails g migration add_email_to_users email:string

Inside the Generated Migration File

This will generate a migration file with the following code:

class AddEmailToUsers < ActiveRecord::Migration[6.0]
  def change
    add_column :users, :email, :string
  end
end

The “add_column” method is provided by the Rails migration library and is used to add a new column to a table. The first argument is the name of the table, the second argument is the name of the column, and the third argument is the data type of the column.

Running the Migration

Once you have generated the migration file, you need to run it using the “rails db:migrate” command. This will execute the code in the migration file and add the new column to the database.

rails db:migrate

Importance of Rails Migrations

Rails migrations are important because they allow you to easily track and revert changes to the database over time. When you run a migration, Rails updates a special table in the database called the “schema_migrations” table to keep track of which migrations have been run. This ensures that you can roll back changes to the database if necessary.