I am trying to update the changed date of a table. For instance, I have a table with 4 columns: column1, column2, column3, changed_dt.
If any of the first 3 columns get update, I want the changed date to update.

Code:
CREATE TRIGGER MyTestTrigger
    AFTER UPDATE of "column1", "column2", "column3"
    ON Mytable REFERENCING OLD AS OLD NEW AS NEW
    FOR EACH ROW
...