When did Deng Xuan first win Women's singles?
CREATE TABLE "previous_winners" (
  "year" real,
  "men_s_singles" text,
  "women_s_singles" text,
  "men_s_doubles" text,
  "women_s_doubles" text,
  "mixed_doubles" text
);
SELECT MIN("year") FROM "previous_winners" WHERE "women_s_singles"='deng xuan';