Need help on Null value check function

Question

Hey guys,
I need to create a function that will accept two values and perform a comparison on them and based on whether or not they're different, return true or false.
Initially I had no idea about the problems of comparing when a value was null, hence the need for a function, as I need to compare many fields of rows of a table in order to find what has changed.
Now, I think I have the NULL check logic in place :
IF R1.X IS NULL THEN
     IF R2.X IS NULL THEN
          RETURN FALSE; -- both R1 and R2 are null so no diffs
     ELSE
          RETURN TRUE; -- R1 is null but R2 is not, so it's a diff
     END IF;
ELSE
     IF R2.X IS NULL THEN
          RETURN TRUE; -- R1 is not null but R2 is so a diff
     ELSE
          IF R1.X != R2.X THEN
               RETURN TRUE; -- both not null but different
          ELSE
               RETURN FALSE; -- both not null but equal
          END IF;
     END IF;
END IF;My problem is that I don't know how, or if i can, create function that can simply accept two column values without defining their datatypes in the function sig. Reason being that while I will always be comparing like-for-like datatypes, I won't always be comparing the "same" like-for-like datatypes; so as I loop through 100 table rows (differentiated by a date), I'll physically compare all the fields in the rows one by one, and in one instance i'm comapring two NUMBERs and then two VARCHARs and then two DATEs, etc.
What i didn't want was duplicate func's that are all the same apart from the sig's.
Is there an easy(ier) way to accomplish this? Is there a more "generic" value type I could use? basically i just want to have a function like :
CREATE OR REPLACE FUNCTION(val1 VALUE, val2 VALUE)
And not multiple like :
CREATE OR REPLACE FUNCTION(val1 NUMBER, val2 NUMBER)
CREATE OR REPLACE FUNCTION(val1 DATE, val2 DATE)
and so on.
Edited by: user11258962 on 28-Jun-2010 09:02

Answer 1

You can use function overloading. So, although three function will exist, they will all be called the same name, so your code will always call a single function
create or replace package pkg_compare as
  function is_Alike (p1 in number
                    ,p2 in number) return boolean ; 
  function is_Alike (p1 in varchar2
                    ,p2 in varchar2) return boolean; 
  function is_Alike (p1 in date
                    ,p2 in date) return boolean; 
end pkg_Compare;
create or replace package body pkg_compare as
  function is_Alike (p1 in number
                    ,p2 in number) return boolean as
    begin
      return ( nvl(p1,0) = nvl(p2,-1) );
  end is_Alike;
  function is_Alike (p1 in varchar2
                    ,p2 in varchar2) return boolean as
    begin
      return ( nvl(p1,'X') = nvl(p2,'Z') );
  end is_Alike;
  function is_Alike (p1 in date
                    ,p2 in date) return boolean as
    begin
      return ( nvl(p1,sysdate) = nvl(p2,sysdate-1) );
  end is_Alike;
end pkg_Compare;
/