CREATE TABLE "21st_century" (
  "year" real,
  "men_s_singles" text,
  "women_s_singles" text,
  "men_s_doubles" text,
  "women_s_doubles" text,
  "mixed_doubles" text
);

Question: Which women's doubles had the accompanying Men's singles player Ville Lång?
SQL: SELECT "women_s_doubles" FROM "21st_century" WHERE "men_s_singles"='ville lång';

Question: Which mixed doubles was featured in 2006?
SQL: SELECT "mixed_doubles" FROM "21st_century" WHERE "year"=2006;

Question: Which women's doubles had the men's singles player Kenichi Tago?
SQL: SELECT "women_s_doubles" FROM "21st_century" WHERE "men_s_singles"='kenichi tago';