user: Question: What was the margin of victory when the winning score was −12 (66-67-64-71=268)?
Columns: ['Date', 'Tournament', 'Winning score', 'Margin of victory', 'Runner(s)-up']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['May 22, 1994', 'Memorial Tournament', '−20 (67-67-67-67=268)', '5 strokes', 'Greg Norman']
SQL:

assistant: SELECT "Margin of victory" FROM "Table" WHERE "Winning score" = '−12 (66-67-64-71=268)';