[sql] How can you tell if a value is not numeric in Oracle?

I have the following code that returns an error message if my value is invalid. I would like to give the same error message if the value given is not numeric.

IF(option_id = 0021) THEN 
      IF((value<10000) or (value>7200000) or /* Numeric Check */)THEN
          ip_msg(6214,option_name);  -- Error Message
          return;
      END IF;
END IF;      

In SQL Server, I simply used ISNUMERIC(). I would like to do something similar in Oracle. Such as,

IF((!ISNUMERIC(value)) or (value<10000) or (value>7200000))
    THEN ...

There is no built-in function. You could write one

CREATE FUNCTION is_numeric( p_str IN VARCHAR2 )
  RETURN NUMBER
IS
  l_num NUMBER;
BEGIN
  l_num := to_number( p_str );
  RETURN 1;
EXCEPTION
  WHEN value_error
  THEN
    RETURN 0;
END;

and/or

CREATE FUNCTION my_to_number( p_str IN VARCHAR2 )
  RETURN NUMBER
IS
  l_num NUMBER;
BEGIN
  l_num := to_number( p_str );
  RETURN l_num;
EXCEPTION
  WHEN value_error
  THEN
    RETURN NULL;
END;

You can then do

IF( is_numeric( str ) = 1 AND 
    my_to_number( str ) >= 1000 AND
    my_to_number( str ) <= 7000 )

If you happen to be using Oracle 12.2 or later, there are enhancements to the to_number function that you could leverage

IF( to_number( str default null on conversion error ) >= 1000 AND
    to_number( str default null on conversion error ) <= 7000 )

You can use the following regular expression which will match integers (e.g., 123), floating-point numbers (12.3), and numbers with exponents (1.2e3):

^-?\d*\.?\d+([eE]-?\d+)?$

If you want to accept + signs as well as - signs (as Oracle does with TO_NUMBER()), you can change each occurrence of - above to [+-]. So you might rewrite your block of code above as follows:

IF (option_id = 0021) THEN 
    IF NOT REGEXP_LIKE(value, '^[+-]?\d*\.?\d+([eE][+-]?\d+)?$') OR TO_NUMBER(value) < 10000 OR TO_NUMBER(value) > 7200000 THEN
        ip_msg(6214,option_name);
        RETURN;
    END IF;
END IF;

I am not altogether certain that would handle all values so you may want to add an EXCEPTION block or write a custom to_number() function as @JustinCave suggests.

The best answer I found on internet:

SELECT case when trim(TRANSLATE(col1, '0123456789-,.', ' ')) is null
            then 'numeric'
            else 'alpha'
       end
FROM tab1;

CREATE OR REPLACE FUNCTION IS_NUMERIC(P_INPUT IN VARCHAR2) RETURN INTEGER IS
  RESULT INTEGER;
  NUM NUMBER ;
BEGIN
  NUM:=TO_NUMBER(P_INPUT);
  RETURN 1;
EXCEPTION WHEN OTHERS THEN
  RETURN 0;
END IS_NUMERIC;
/

From Oracle DB 12c Release 2 you could use VALIDATE_CONVERSION function:

VALIDATE_CONVERSION determines whether expr can be converted to the specified data type. If expr can be successfully converted, then this function returns 1; otherwise, this function returns 0. If expr evaluates to null, then this function returns 1. If an error occurs while evaluating expr, then this function returns the error.

 IF (VALIDATE_CONVERSION(value AS NUMBER) = 1) THEN
     ...
 END IF;

db<>fiddle demo

SELECT DECODE(REGEXP_COUNT(:value,'\d'),LENGTH(:value),'Y','N') AS is_numeric FROM dual;

There are many ways but this one works perfect for me.