SQL Qeury Is Number Function

Why need Is Number function?

Is_Number function, can help you to check a Value it's number or char. if a value is a number the result will return True, else return FALSE.

Example: 

select * from sttm_customer c 

where is_number(c.unique_id_value)='Y';

 How to create Function "is_number"?

Query:

CREATE OR REPLACE FUNCTION is_number( p_str IN VARCHAR2 )

  RETURN VARCHAR2 DETERMINISTIC PARALLEL_ENABLE
IS
  l_num NUMBER;
BEGIN
  l_num := to_number( p_str );
  RETURN 'Y';
EXCEPTION
  WHEN value_error THEN
IS_NUMBER    RETURN 'N';
END is_number;