create table tab (
	id int primary key,
	field char,
	dt datetime year to second default current year to second
);

insert into tab ( id, field ) values (  1 , 'A' );
insert into tab ( id, field ) values (  2 , 'B' );
insert into tab ( id, field ) values (  3 , 'C' );
insert into tab ( id, field ) values (  4 , 'D' );
insert into tab ( id, field ) values (  5 , 'E' );

create trigger tab_up update on tab
for each row (
	-- а вот что здесь написать, никак не пойму
);

create procedure get_current( ) returning datetime year to second;
	return current;
end procedure;
create trigger tab_up update on tab referencing new as new
for each row (
	execute procedure get_current( ) into new.dt
);

QUERY:
------
update tab set field = 'X' where id = 1
Estimated Cost: 1
Estimated # of Rows Returned: 1
  1) informix.tab: INDEX PATH
    (1) Index Keys: id   (Serial, fragments: ALL)
        Lower Index Filter: informix.tab.id = 1 
QUERY:
------

Estimated Cost: 1
Estimated # of Rows Returned: 5
  1) informix. tab :  SEQUENTIAL SCAN 
UDRs in query:
--------------
    UDR id  :	3500
    UDR name:	get_current

QUERY:
------
update tab set field = 'X' where id = 10000001
Estimated Cost: 1
Estimated # of Rows Returned: 1
  1) informix.tab: INDEX PATH
    (1) Index Keys: id   (Serial, fragments: ALL)
        Lower Index Filter: informix.tab.id = 10000001 
QUERY:
------

Estimated Cost: 72964
Estimated # of Rows Returned: 2134446
  1) informix.tab: SEQUENTIAL SCAN
UDRs in query:
--------------
    UDR id  :	234
    UDR name:	get_current