Ungetestet im Prinzip so:
SQL-Code:
select distinct a.nr, a.name
from beh a
left join qundz b on (b.ziel = a.nr)
left join beh c on (c.nr = b.quelle) and (c.rohstoff = :rohstoff1)
left join beh d on (d.nr = b.quelle) and (d.rohstoff = :rohstoff2)
left join beh e on (e.nr = b.quelle) and (e.rohstoff = :rohstoff3)
where (c.nr is not null) and (d.nr is not null) and (e.nr is not null)