```ruby
class CreateUserProjects < ActiveRecord::Migration
  def change
    create_table :user_projects do |t|
      t.integer :user_id, null: false
      t.integer :project_id, null: false

      t.timestamps null: false
    end
  end
end
```

Add access field to user project
user
```ruby
class CreateUserProjects < ActiveRecord::Migration
  def change
    create_table :user_projects do |t|
      t.integer :user_id, null: false
      t.integer :project_id, null: false
      t.string :access, null: false

      t.timestamps null: false
    end
  end
end
```
assistant