Rails Migration: Remove Default

Rails provides us with an easy way to modify the database schema using Migrations. With migrations, we can add and remove columns, indexes and even entire tables from our database.

In this article, we'll focus on the remove_column method that allows us to remove a column from a table.

Creating a Migration

To remove a column from a table, we first need to create a migration for it using the rails generate command. Here's the command that creates a migration to remove a default value from a column:

rails g migration remove_default_from_column

This will generate a new migration file with a timestamp in the file name. Next, we need to open the migration file and edit the change method.

Removing Default Value from Column

To remove a default value from a column, we need to use the remove_column method inside the change method of the migration. Here's an example:

class RemoveDefaultFromColumn < ActiveRecord::Migration[6.1]
  def change
    remove_column :users, :age, :integer, default: 0
  end
end

In this example, we're removing the default value of 0 from the age column of the users table.

The remove_column method takes three arguments:

• the name of the table
• the name of the column
• the data type of the column (optional)

Running the Migration

Once we've created the migration file and edited the change method, we can run the migration using the rails db:migrate command. This will execute the change method and remove the default value from the column.

rails db:migrate

Conclusion

In this article, we learned how to remove a default value from a column in a database table using Rails Migrations. By following these steps, we can easily modify the database schema and keep our application up-to-date with changing business requirements.