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 Women's singles in 2013?
SQL: SELECT "women_s_singles" FROM "previous_winners" WHERE "year"='2013';

Question: Who won the Men's doubles when there was no competition in the Men's singles?
SQL: SELECT "men_s_doubles" FROM "previous_winners" WHERE "men_s_singles"='no competition';

Question: What year was there no competition in Mixed Doubles?
SQL: SELECT "year" FROM "previous_winners" WHERE "mixed_doubles"='no competition';

Question: What year did Lonneke Janssen win the Women's singles?
SQL: SELECT "year" FROM "previous_winners" WHERE "women_s_singles"='lonneke janssen';