TRIGGER en oracle 10g.

[todoaeropuertos]

Hola:

Conseguí que me funcionara cambiando AFTER por BEFORE

create or replace trigger promedio
before update or insert on mitabla
for each row
declare
media number;
begin
select ((:new.c1 + :new.c2)/2)
into media
from dual;
:new.media := media;
end;