You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: 20181109183821_update_users_current_user_role_id_with_wrong_unity_id.rb
    path of file: ./repos/i-diario/db/migrate
    
    the code of the file until where you have to start completion: class UpdateUsersCurrentUserRoleIdWithWrongUnityId 
    
  def change
    execute <<-SQL
      UPDATE users
        SET current_user_role_id = NULL
      WHERE EXISTS(
              SELECT 1
                FROM user_roles
               WHERE user_roles.id = users.current_user_role_id
                 AND user_roles.unity_id <> users.current_unity_id
            )
    SQL
  end