我不断收到错误ORA-01422，ORA-06512

Question

I keep getting error ORA-01422: exact fetch returns more than requested number of rows. ORA-06512: at "CM420A07.ZIP_CODE_SALES_WINNER", line 6. I cannot figure out exactly what is going wrong.

CREATE OR REPLACE FUNCTION ZIP_CODE_SALES_WINNER
  RETURN VARCHAR
IS
  zipWinner VARCHAR2(5);
BEGIN
  SELECT C.zip_code INTO zipWinner
  FROM SALE S JOIN CUSTOMER C
  ON S.cust_ID = C.cust_ID
  GROUP BY C.zip_code
  HAVING COUNT(*) = (
  SELECT MAX(COUNT(*))
  FROM SALE S JOIN CUSTOMER C
  ON S.cust_ID = C.cust_ID
  GROUP BY C.zip_code);  
  RETURN zipWinner;
END;
/
SELECT ZIP_CODE_SALES_WINNER FROM DUAL;

Answer 1

Your query returns more than one value.

If you do not care which zipcode will be selected if there is more than one just add rownum=1 to the query to get exactly one row:

SELECT zip_code INTO zipWinner FROM (
SELECT C.zip_code 
  FROM SALE S JOIN CUSTOMER C
  ON S.cust_ID = C.cust_ID
  GROUP BY C.zip_code
  HAVING COUNT(*) = (
  SELECT MAX(COUNT(*))
  FROM SALE S JOIN CUSTOMER C
  ON S.cust_ID = C.cust_ID
  GROUP BY C.zip_code))
  WHERE  rownum =1;