Looks like a bug in DB, Getting a invalid number with a group by

Question

Hi All,
This is very strange problem that I am encountering. Would like to hear from you, if you have also witnessed something similar:
What I am doing:
basically I am doing something like:
Select x,y,z,count(distinct a) from
taba,tabb,(select col1,col2 from tabc) tc,
tabd left outer join tabe on tabd.col=tabe.col,
viewf
where (joins between the tabs)
group by x,y,z
All the join columns are number(10,0) in all the tables/views.
If I run this query I get an invalid number 01722. If I comment the count(distinct a) column, the query runs fine.
Or if I put the to_number for all the joined columns in the where clause, the query runs fine.
I have never seen such behaviour of Oracle database. May be I am doing something really wrong?
Looking for help.
Thanks in advance.

Answer 1

Well, I do not think it is related to GROUP BY or to DISTINCT. Most likely you have some column X that holds both numeric and non-numeric strings and some other column that indicates if column X value is numeric. If this is the case, you can get ORA-01722 simply becuase Oracle does not apply where clause predicates in the order they are listed. Assume column c1 holds numeric strings when column c2 is set to some specific value. Even if you use:
WHERE c2 = 'some-value'
AND TO_NUMBER(c1) = 5
it is not guaranteed Oracle will first check c2 and only then c1. And if Oracle decides to check c1 first, TO_NUMBER will fail on the first non-numeric c1. Especially it can happen in not very recent Oracle versions. In recent versions most of the time optimizer is smart enough to realize that checking c2 costs less that converting c1 to number and then checking it, so it will check c2 first. Anyway, you need to use ORDERED_PREDICATES hint to let optimizer know to follow predicate sequence. For example, in 9i:
SQL> create table tbx(flag varchar2(6),value varchar2(10))
  2  /
Table created.
SQL> insert into tbx values('alpha','abc');
1 row created.
SQL> insert into tbx values('number','123');
1 row created.
SQL> commit;
Commit complete.
SQL> select * from tbx
  2  where flag = 'number' and value = 123
  3  /
where flag = 'number' and value = 123
ERROR at line 2:
ORA-01722: invalid number
SQL> select /*+ ORDERED_PREDICATES */ * from tbx
  2  where flag = 'number' and value = 123
  3  /
FLAG   VALUE
number 123
SQL>SY.