CREATE TABLE "past_winners" (
  "year" real,
  "mens_singles" text,
  "womens_singles" text,
  "mens_doubles" text,
  "womens_doubles" text,
  "mixed_doubles" text
);

Question: What was the competition when there was no competition for mens doubles?
SQL: SELECT "womens_doubles" FROM "past_winners" WHERE "mens_doubles"='No competition';

Question: Who won the mixed doubles in 1998?
SQL: SELECT "mixed_doubles" FROM "past_winners" WHERE "year"=1998;