Verifing the data type

Question

Hi,
I'd like to know how can I verify if the variable contains only the data type that I'm expecting for. In SQLSERVER we have the IS_NUMERIC, IS_CHAR... functions. Is there something similar in ORACLE? How can I use it?
Thanks.

Answer 1

It is easy enough to test whether a value is numeric. You can create a function like:
CREATE OR REPLACE FUNCTION IS_NUMBER (p_test_val IN VARCHAR2)
RETURN BOOLEAN IS
l_t_val NUMBER;
BEGIN
   l_t_val := TO_NUMBER(p_test_val);
   RETURN TRUE;
EXCEPTION WHEN VALUE_ERROR THEN
   RETURN FALSE;
END;This attempts to convert the value passed in (note that the parameter is a character type) to a number. If it suceeds, then it retrns TRUE. If the conversion causes an error, then the exception handler catches it and returns FALSE.
The BOOLEAN data type is only valid in PL/SQL (and probably other host languages like C or Java), you cannot use this function in a SQL statement. To use this in a SQL statement, then you would need to change the return type to number, and return something like 1 for TRUE and 0 for FALSE.
To use the function in a PL/SQL procedure, you could do something like:
DECLARE
l_val_to_test VARCHAR2(10) := '123';
BEGIN
   IF is_number (l_val_to_test) THEN
      DBMS_OUTPUT.Put_Line ('Value is a number');
   ELSE
      DBMS_OUTPUT.Put_Line ('Value is not a number');
   END IF;
END;Which would return TRUE.
TTFN
John