```ruby
class AddProjectNameToTeams < ActiveRecord::Migration
  def up
    add_column :teams, :project_name, :string

    Project.joins(:team).each do |project|
      project.team.update_column :project_name, project.name
    end
  end

  def down
    remove_column :teams, :project_name
  end
end
```

Allow running migrations when association is gone
user
```ruby
class AddProjectNameToTeams < ActiveRecord::Migration
  def up
    add_column :teams, :project_name, :string

    Project.joins(:team).each do |project|
      project.team.update_column :project_name, project.name
    end if Project.new.respond_to? :team
  end

  def down
    remove_column :teams, :project_name
  end
end
```
assistant