Can we run this statement

Question

Can we use this SQL statement and create a sum
select WHSE_DBA.FLIGHT_ACTIVITY.rental_cost,
WHSE_DBA.FUEL_PURCHASE.actual_cost,
WHSE_DBA.FUEL_PURCHASE.unit_cost,
WHSE_DBA.FUEL_PURCHASE.total_cost,
sum(WHSE_DBA.FLIGHT_ACTIVITY.rental_cost+
WHSE_DBA.FUEL_PURCHASE.actual_cost+
WHSE_DBA.FUEL_PURCHASE.unit_cost+
WHSE_DBA.FUEL_PURCHASE.total_cost) as Total_Cost from
WHSE_DBA.FLIGHT_ACTIVITY,
WHSE_DBA.FUEL_PURCHASE
where WHSE_DBA.FLIGHT_ACTIVITY.SRC_CONTROL_NO=WHSE_DBA.FUEL_PURCHASE.SRC_CONTROL_NO
group by
rental_cost,actual_cost,unit_cost,total_cost

Answer 1

Hi,
As Rkhtsen said, one of the columns you're trying to SUM is a VARCHAR2 or other string. If that's the case, and the column is supposed to contain the string representation of a number (a very bad idea because it causes this problem), then you have to figure out what the bad data is, and clean it up.
This function can help.
CREATE OR REPLACE FUNCTION  to_num
    in_num_text  IN  VARCHAR2,
    in_fmt_text  IN  VARCHAR2
                     DEFAULT NULL
RETURN  NUMBER
--  **  t o _ n u m  **
--  to_num returns the value of in_num_text if it is a number in
--    the format specified by in_fmt_text, NULL if it is not.
--  If in_fmt_text is omitted, to_num will return a number if
--    in_num_text is a number in ANY usual format, e.g. '5', '+5',
--    '5.00', '.5e1' all return 5.
IS
BEGIN
    IF  in_fmt_text  IS NULL
    THEN
        RETURN  TO_NUMBER ( in_num_text );
    ELSE
        RETURN  TO_NUMBER ( in_num_text
                          , in_fmt_text
    END IF;
EXCEPTION
    WHEN OTHERS
    THEN
        RETURN  NULL;
END   to_num;
/For example, say that you learn that flight_activity.rental_cost is a VARCHAR2 column. The following query will show all the values from that table that are not valid numbers:
SELECT  rental_cost
FROM    flight_activity
WHERE   rental_cost         IS NOT NULL
  AND   to_num (rental_cost) IS NULL;If this query produces any rows, that's what's causing the problem. (The same problem may exist in other tables, too.) Either fix the rows shown, or, if it's legitimate to ignore them, use to_num (rental_cost) instead of rental_cost in your SUM.