SELECT winning_score FROM table_name_27 WHERE margin_of_victory = "1 stroke" AND runner_s__up = "robert-jan derksen"
Berapa skor kemenangan di mana runner-up adalah Robert-Jan Derksen dan Margin of Victory adalah 1 stroke?
CREATE TABLE table_name_27 (winning_score VARCHAR, margin_of_victory VARCHAR, runner_s__up VARCHAR)