How many years did Peter Mikkelsen win the Mens Singles?
CREATE TABLE "previous_winners" (
  "year" real,
  "mens_singles" text,
  "womens_singles" text,
  "mens_doubles" text,
  "womens_doubles" text,
  "mixed_doubles" text
);
SELECT COUNT("year") FROM "previous_winners" WHERE "mens_singles"='Peter Mikkelsen';