user: Question: What is the winning score where the runner-up is Robert-Jan Derksen and the margin of victory is 1 stroke?
Columns: ['Date', 'Tournament', 'Winning score', 'Margin of victory', 'Runner(s)-up']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['10 Oct 1993', 'Alfred Dunhill Open', '–14 (68-68-66-68=270)', '2 strokes', 'Nick Faldo , Vijay Singh']
SQL:

assistant: SELECT "Winning score" FROM "Table" WHERE "Margin of victory" = '1 stroke' AND "Runner(s)-up" = 'Robert-Jan Derksen';