oracle numeric condition check

Hi Team,

 I have an requirement , where in I need to check whether the numeric fields in the table are having numeric  values or  not. If not  then I need to update the status to E which means error.

Here again what is the best solution , the reason being if I use the

Select to_number(internal_key,'9999999999') from dual , if the internal_key column has character value then it will throw an error and
will not be able to update the table.


 table name
 test_data


 employeeID                    NUMBER      
 internal_KEY                 VARCHAR2(10)  
 band_ID                   VARCHAR2(38)  
 appraisal_score       DECIMAL(2,5)  
 salary     VARCHAR2(10)  
 STATUS                       CHAR(1)      
 ERROR_CODE                   VARCHAR2(15)
 ERROR_DESC                   VARCHAR2(1000)