To_number function and the "invalid number" error

Question

Dear all,
I have searched the forum for threads relating to the ORA-01722: invalid number error, could not find the answer I am looking for.
What I was trying to do was
select * from table1 where to_number(field1) > 1000
field1 is a varchar2 data type.
I tried all sorts of things i.e using fmt, nls params as defined in the documentation, nothing worked.
Though the practical problem was solved by
select * from table1 where field1 > '1000'
I would still like to know why this error occurs. Can someone help ?
Regards
Crusoe

Answer 1

I think the database engine should simply return the rows that successfully convert to number and meet the where condition Oracle does not work in that way ;)
Then try this...
Just you need to add the below where clause to your source query. as this will retrieve only the number, to_number should work without any problem.
But still you have to create a subquery to escape the invalid number error.
PRAZY@11gR1> select * from tablea;
FIELD1
123
123.345
45
AVC
23.234.234
ABC.234
345.45
7 rows selected.
Elapsed: 00:00:00.00
PRAZY@11gR1> select to_number(field1) from tablea where  rtrim(trim(regexp_replace(field1,'\.','',1,1)),'0123456789') is null;
TO_NUMBER(FIELD1)
              123
          123.345
               45
           345.45
4 rows selected.
Elapsed: 00:00:00.01Regards,
Prazy
Edited by: Prazy on Mar 23, 2010 4:00 PM