CREATE TABLE "previous_winners" (
  "year" text,
  "men_s_singles" text,
  "women_s_singles" text,
  "men_s_doubles" text,
  "women_s_doubles" text,
  "mixed_doubles" text
);

Question: Who won the mixed doubles the same year that Andrew Downes won the men's singles?
SQL: SELECT "mixed_doubles" FROM "previous_winners" WHERE "men_s_singles"='andrew downes';

Question: Who won the mixed doubles in the years that the men's doubles has no competition?
SQL: SELECT "mixed_doubles" FROM "previous_winners" WHERE "men_s_doubles"='no competition';