select name, sum(kol) as kolsum from
(select id, kol as total from pr
union all
select id, (kol*- 1 ) as total from ras) as t inner join tovar
on t.id=tovar.id
group by name

select katalog.name, sum(t.total) as kolsum from
(select id, kol as total from pr
union all
select id, (kol*- 1 ) as total from ras) as t inner join katalog 
on t.id=katalog.id
group by katalog.name

select katalog.name, sum(t.total) as kolsum from
(select id_katalog, kol as total from pr
union all
select id_katalog, (kol*- 1 ) as total from ras) as t inner join katalog 
on t.id_katalog=katalog.id
group by katalog.name

select katalog.id, katalog.name, nz(sum(pr.kol), 0 )-nz(sum(ras.kol), 0 ) as ost
from katalog
left join pr on katalog.id = pr.id_katalog
left join ras on katalog.id = ras.id_katalog
group by katalog.id, katalog.name