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

Question: When did Chetan Anand win his first men's single?
SQL: SELECT MIN("year") FROM "previous_winners" WHERE "mens_singles"='Chetan Anand';

Question: How many times did Niels Christian Kaldau win the men's single and Pi Hongyan win the women's single in the same year?
SQL: SELECT COUNT("year") FROM "previous_winners" WHERE "mens_singles"='Niels Christian Kaldau' AND "womens_singles"='Pi Hongyan';

Question: Who won the men's double when Chou Tien-Chen won the men's single?
SQL: SELECT "mens_doubles" FROM "previous_winners" WHERE "mens_singles"='Chou Tien-chen';