Who won the mens doubles at the 2006 guangzhou event?
CREATE TABLE "china_open" (
  "year_location" text,
  "mens_singles" text,
  "womens_singles" text,
  "mens_doubles" text,
  "womens_doubles" text
);
SELECT "mens_doubles" FROM "china_open" WHERE "year_location"='2006 Guangzhou';