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
);

Question: In which women's doubles did Wang Junjie play men's singles?
SQL: SELECT "women_s_doubles" FROM "previous_winners" WHERE "men_s_singles"='wang junjie';

Question: In what mixed doubles did Niels Christian Kaldau play in men's singles?
SQL: SELECT "mixed_doubles" FROM "previous_winners" WHERE "men_s_singles"='niels christian kaldau';

Question: Which mixed doubles happened later than 2011?
SQL: SELECT "mixed_doubles" FROM "previous_winners" WHERE "year">2011;