I hope this is usefull. Like I said, I created a workaround using a database trigger. My core skills are java, jsf, (PL)/SQL. I'm just starting out with Joomla and php.
translated the joomla table prefix to #_
create trigger event_after_insert after
insert
on
#__jevents_vevent for each row begin
-- code:
if not exists
(
select
1
from
#__jevents_catmap cm
where
cm.evid = new.ev_id
and cm.catid = new.catid
)
then
insert
into
#__jevents_catmap
(
evid,
catid,
ordering
)
values
(
new.ev_id,
new.catid,
0
) ;
end if;
end;