oracle trigger 更新指定一个字段时同时更新该表另一个字段

CREATE OR REPLACE TRIGGER t_xxx_xxx_trigger
before insert or update of tray_namestate on t_xxx_INFO
FOR EACH ROW
BEGIN
IF :OLD.tray_namestate != :NEW.tray_namestate THEN
:new.input_date := sysdate;
end if;
END;