CREATE TABLE "calendar_winners" (
  "round" real,
  "circuit" text,
  "date" text,
  "class_a_winner" text,
  "class_b_winner" text,
  "class_c_winner" text,
  "class_d_winner" text
);

Question: In which round did Roy Salvadori won Class D and Alan Hutcheson won Class B?
SQL: SELECT "round" FROM "calendar_winners" WHERE "class_d_winner"='Roy Salvadori' AND "class_b_winner"='Alan Hutcheson';

Question: When did Alan Hutcheson won Class B on round 1?
SQL: SELECT "date" FROM "calendar_winners" WHERE "class_b_winner"='Alan Hutcheson' AND "round"=1;