Determining if the Field Data in Oracle is of Number type
Problem
You want to query those only from the varchar2 or char field containing number data with no any other character.
Solution
Create a function to determine this:
Create or Replace Function is_number (iNumber in Varchar2)    Return Varchar2 is nVal Number; Begin   nVal := To_Number(iNumber);  -- if there is no error   Return('TRUE'); Exception  when others then   -- error during conversion   Return('FALSE'); end;
Use in query:
Select Empno, Ename, dummychar   from emp where is_number(dummychar) = 'TRUE';