RosettaCodeData/Task/Fibonacci-sequence/PL-pgSQL/fibonacci-sequence-1.sql

CREATE OR REPLACE FUNCTION fib(n INTEGER) RETURNS INTEGER AS $$
BEGIN
  IF (n < 2) THEN
    RETURN n;
  END IF;
  RETURN fib(n - 1) + fib(n - 2);
END;
$$ LANGUAGE plpgsql;