CREATE TABLE "european_competition_history" (
  "season" text,
  "competition" text,
  "round" text,
  "club" text,
  "home" text,
  "away" text,
  "aggregate" text
);

Question: The Crvena Zvezda club has what aggregate?
SQL: SELECT "aggregate" FROM "european_competition_history" WHERE "club"='crvena zvezda';