Encountered ORA-01722 Invalid number when query doc from view

Question

Hi all,
I have the following view.
Select item, to_number(wo) a
from tablea
union all
select item, wo
from tablebb
The problem rise ( ORA-01722) when I try to search for wo from the view after the view has been created. The wo field in tablea was varchar2 where user will key in the number only. And wo in tabebb is number, I can't change the column format as it is belong the my standard application table. How to solve this problem ?
Thanks
Lim

Answer 1

sm**** wrote:
I try to simplified my query. In fact, there are several where clause for both tables. The reason is because of the varchar2 field in WO at tablea versus the numeric field in WO for tableb. OK. The problem then is almost certainly that you have non-numeric characters in the column but you don't happen to have non-numeric characters in the columns that match all the other predicates.
Oracle is free to apply the TO_NUMBER function before it applies some or all of the predicates you specify in your WHERE clause. If it happens to apply the TO_NUMBER on a row that has non-numeric data before it applies the condition in the WHERE clause that filters out that particular row, you'll get an error. If, on the other hand, Oracle happens to filter out the row before applying the TO_NUMBER, you'll get the results you expect. It all comes down to which plan Oracle picks. But, in general, there is no guarantee about whether you'll get an error or whether you'll get the data you want.
You can define your own function
CREATE OR REPLACE FUNCTION my_to_number( p_str IN VARCHAR2 )
  RETURN number
IS
  l_num NUMBER;
BEGIN
  l_num := to_number( p_str );
  RETURN l_num;
EXCEPTION
  WHEN others THEN
    RETURN null;
END;and use that instead of to_number in your query. That will catch the exception if the function is applied to a row before one of the predicates is applied.
Justin