What is the Season when league shows bundesliga, and a European competition of played korac cup?
CREATE TABLE "season_by_season" (
  "season" text,
  "tier" real,
  "league" text,
  "postseason" text,
  "european_competitions" text
);
SELECT "season" FROM "season_by_season" WHERE "league"='bundesliga' AND "european_competitions"='played korac cup';