How many years have a Pick of 12, and a Position of dt, and a College of penn state?
CREATE TABLE "player_selection" (
  "year" real,
  "pick" text,
  "player" text,
  "position" text,
  "college" text
);
SELECT COUNT("year") FROM "player_selection" WHERE "pick"='12' AND "position"='dt' AND "college"='penn state';