How to track a column is not updated in a update statement issued.

Question

Hello All,
Is there a way to write a trigger when a particular column is not specified in update statement.
For example, consider i have a table with 20 columns(Say Column1...column20). Trigger has to get fired only when column15(say) is not specified.
I know
CREATE OR REPLACE TRIGGER test_trigger
BEFORE UPDATE
OF COLUMN1, COLUMN2......COLUMN20--Except COLUMN15
ON TESTTABLE
FOR EACH ROW
BEGIN
END of_clause; /
above trigger will solve my problem. But i don't want to mention all columns in this trigger. It will cause maintainance problem afterwards.
Is there any way to mention something like NOT OF COLUMN in the trigger ?
Regards,
Abhijit.

Answer 1

That trigger would get fired for every column except column 15.
What do you mean by "when a particular column is not specified in update statement"? Do you mean that the column is not mentioned at all in the update statement, or that the value of that column is not being changed even if it is mentioned in the statement?
If you mean the former, then I don't think there is any way to do that. however, if you want to do something only if the value in column15 is unchanged, then something along the lines of:
CREATE TRIGGER test_trigger
   BEFORE UPDATE OF testtable
   FOR EACH ROW
BEGIN
BEGIN
   IF (:new.column15 IS NULL and :old.column15 IS NULL) OR
      (:new.column15 IS NOT NULL and :old.column15 IS NOT NULL and
       :new.column15 = :old.column15) THEN
      < do whatever for no changes >
   ELSE
      < do nothing or something else for changes >
   END IF;
END;John