What was the playoff apps for Thomas Heary, that had the position df?
CREATE TABLE "appearances_and_goals" (
  "squad_no" real,
  "name" text,
  "position" text,
  "league_apps" text,
  "league_goals" real,
  "fa_cup_apps" text,
  "fa_cup_goals" real,
  "league_cup_apps" text,
  "league_cup_goals" real,
  "flt_apps" text,
  "flt_goals" real,
  "playoff_apps" text,
  "playoff_goals" real,
  "total_apps" text,
  "total_goals" real
);
SELECT "playoff_apps" FROM "appearances_and_goals" WHERE "position"='df' AND "name"='thomas heary';