when mixed doubles is zheng bo ma jin and womens singles is wang yihan, what was the tour?
CREATE TABLE "winners" (
  "tour" text,
  "mens_singles" text,
  "womens_singles" text,
  "mens_doubles" text,
  "womens_doubles" text,
  "mixed_doubles" text
);
SELECT "tour" FROM "winners" WHERE "mixed_doubles"='Zheng Bo Ma Jin' AND "womens_singles"='Wang Yihan';