it's not pretty, and it's probably not efficient, but it works.
Code:
select
items.id, items.name
from
items
left outer join
merchantlist
on
items.id = merchantlist.item
inner join
spells_new as spells
on
substr(items.name from 8) = spells.name
where
scrolltype = 7
and
merchantlist.item is null
and
(classes1 < 75 or
classes2 < 75 or
classes3 < 75 or
classes4 < 75 or
classes5 < 75 or
classes6 < 75 or
classes7 < 75 or
classes8 < 75 or
classes9 < 75 or
classes10 < 75 or
classes11 < 75 or
classes12 < 75 or
classes13 < 75 or
classes14 < 75 or
classes15 < 75 or
classes16 < 75)
order by
items.name;
this should show you a list of item ids and scroll names for all spells below level 75 (change the number to whatever you want) that aren't available on merchants. took just over 22 seconds to run on my slow ass laptop with a number of other things open in the background.