Oracle 21c

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CREATE TABLE Rating (NumberStars NUMBER, customer_ID NUMBER, Tutor_ID NUMBER);
CREATE OR REPLACE FUNCTION averageRating (tutorrating        IN  NUMBER, 
                                          total_count_Rating OUT NUMBER)
RETURN NUMBER
IS
    countRating    NUMBER;
    averages       NUMBER;
    too_few_data   EXCEPTION;
BEGIN
     SELECT AVG(NumberStars), count(customer_ID)
       INTO averages, countRating
       FROM Rating 
      WHERE Tutor_ID  = tutorrating;

     IF countRating <= 1 THEN
        RAISE too_few_data;
     END IF;

     total_count_Rating := countRating;
     
Return averages;

EXCEPTION
         WHEN too_few_data THEN
              DBMS_OUTPUT.PUT_LINE('Rating is too few.');
              total_count_Rating := 0;
              RETURN 0;
END averageRating;
/
INSERT INTO Rating VALUES (1, 1, 1);
1 rows affected

DECLARE
averages number;
countRating NUMBER;
BEGIN
averages := averageRating(1, countRating);
dbms_output.put_line('The averageRating is:' || averages);
dbms_output.put_line('The number of ratings is:' || countRating);
END;
/
1 rows affected

dbms_output:
Rating is too few.
The averageRating is:0
The number of ratings is:0