How to avoid oracle implicit data type conversion

Question

Hello,
i have a query like below..
SELECT EMP_NUM
FROM EMPLOYEE
WHERE EMP_NUM=SOURCE_EMP_NUM;
1. My SOURCE_EMP_NUM data type is varchar2.
2. My table EMP_NUM data type is number.
3. In one case my SOURCE_EMP_NUM value '00000123'
4. I have an entry in table for EMP_NUM as 123.
5. In this case my query is success and giving me row for 123, which i don't want it should compare with leading zeros. But due to oracle implicit conversion the comparision getting passed.
6. I have an index for this column, so i can't use "like" operator...
Can somebody help me.....
Thanks in adv....

Answer 1

HI,
Just see this :---
SQL> select * from emp where deptno=00020;---------deptno is number, 00020 is number and its true
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
SQL> select * from emp where to_char(deptno)=00020;=-------------deptno is character type and 00020 is number so still it is leaving 0000 from 20 as it number and has no impact,
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
SQL> select * from emp where to_char(deptno)='00020';---now both are character and no row is selected.
no rows selected
So you can avoid the implicit conversion according to the requirements and in this case we are usin to_char function to avoid this.
Regards,
Navneet