No rows returned with where number_value

Question

Hi all,
Im using Oracle 10.2.0.1 on Windows 2000.
I got something strange here.
I have a table like:
TABLE_NAME                     COLUMN_NAME                    DATA_TYPE        DATA_LENGTH DATA_PRECISION DATA_SCALE
TEST                           COL1                           NUMBER                    22           1     0when I try to perform a query like:
select * from test where col = 0this returns 0 rows.
when I do:
select * from test;
      COL1
         1
         1
         1
         1
         0
         0
         2but when a use to_number, it returns rows for zero value:
select * from test where to_number(col) = 0;
      COL1
         0
         0somebody knows about this strange problem?
thank you very much!!!!
[]´s

Answer 1

Hi,
>>I´m trying to understand this.
Me too ;-)
SQL> create table test (col1 number);
Table created.
SQL> alter table test add constraint ck_test check (col1 in ('0','1'));
Table altered.
SQL> insert into test values (0);
1 row created.
SQL> select * from test where col1=0;
no rows selected
SQL> explain plan for select * from test where col1=0;
Explained.
SQL> set linesize 130
SQL> set pagesize 0
SQL> select * from table(dbms_xplan.display);
Plan hash value: 766971379
| Id  | Operation          | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT   |      |     1 |    13 |     0   (0)|          |
|*  1 |  FILTER            |      |       |       |            |          |
|*  2 |   TABLE ACCESS FULL| TEST |     1 |    13 |     3   (0)| 00:00:01 |
Predicate Information (identified by operation id):
1 - filter(NULL IS NOT NULL)
   2 - filter("COL1"=0)
Note
   - dynamic sampling used for this statement
19 rows selected.
SQL> select * from test where to_char(col1)=0;
      COL1
         0
SQL> explain plan for select * from test where to_char(col1)=0;
Explained.
SQL> set linesize 130
SQL> set pagesize 0
SQL> select * from table(dbms_xplan.display);
Plan hash value: 1357081020
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |      |     1 |    13 |     3   (0)| 00:00:01 |
|*  1 |  TABLE ACCESS FULL| TEST |     1 |    13 |     3   (0)| 00:00:01 |
Predicate Information (identified by operation id):
1 - filter(TO_NUMBER(TO_CHAR("COL1"))=0)
Note
   - dynamic sampling used for this statement
17 rows selected.Cheers
Legatti