What is the Margin of Victory, when Tournament is Mercedes Championships (3)?
CREATE TABLE "pga_tour_wins_9" (
  "date" text,
  "tournament" text,
  "winning_score" text,
  "margin_of_victory" text,
  "runner_s_up" text
);
SELECT "margin_of_victory" FROM "pga_tour_wins_9" WHERE "tournament"='mercedes championships (3)';