Compare two columns character by character

Question

Hi
In a form I have block A. Which contains two columns Old Value and New Value both are of varchar datatype. I want to compare Old Value and New Value character by character and display the characters which are there in New Value but not in Old Value in a different colour when this block is being called.
Example1 :Old Value : 13-Jul-2007
And New Value : 19-Jul-2007
I need the output to be display in this way - 19(in different clour)-Jul-2007. Only 9 should be in different colour.
Example2 :Old Value : - (No value Previously)
And New Value : SI DONE
So output to be display in this way New Value "SI DONE" should be in different colour.
Just to hightlight the users that this is change made instead of they manually compare field by field for the changes to take note..
Pls help me this is bit urgent. Help me to suggest any java related coding can help me or any plugins that we can call thru forms to do it.. Pls help.
Rishi

Answer 1

You take a variable i (integer type) and initialize it to 1.
Take a loop where u'll find one by one character in loop as follows.
DECLARE
i NUMBER(10) := 1;
old_str VARCHAR2(240); -- For Old String
new_str VARCHAR2(240); -- For New String
differed_str VARCHAR2(240) := '';
BEGIN
WHILE i <= GREATEST(LENGTH(old_str),LENGTH(new_str))
LOOP
IF SUBSTR(old_str,i,1) <> SUBSTR(new_str,i,1) THEN
differed_str := differed_str||SUBSTR(new_str,i,1);
END IF;
i := i + 1;
END LOOP;
END;
So, now ur extra characters in New Field will be :differed_str.
May be u can give a msg with that string.
Thanx,
Cheers,