user: Question: Who was the runner up when the won by 4 strokes?
Columns: ['No.', 'Date', 'Tournament', 'Winning score', 'To par', 'Margin of victory', 'Runner(s)-up']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '20 Sep 2009', 'Samsung World Championship', '71-67-63-71=272', '–16', '1 stroke', 'Ai Miyazato']
SQL:

assistant: SELECT "Runner(s)-up" FROM "Table" WHERE "Margin of victory" = '4 strokes';