fnrvon     fnran      prozent
----------- ----------- -----------
101             102        5.25
101             103        15.75
101             104        0.00
101             105        0.00
101             106        0.00
101             107        0.00
102             101        5.50
102             103        10.50
102             104        0.00
102             105        0.00
102             106        0.00
102             107        0.00
........

select * from rabatt r1 cross join rabatt r2;

select distinct r1.fnrvon, r2.fnran
    from rabatt r1
    cross join rabatt r2
    where r1.fnrvon != r2.fnran
    order by r1.fnrvon;

SELECT f1.fnr AS 'from', f2.fnr AS 'to', COALESCE(r.prozent, 0)
FROM firma f1
CROSS JOIN firma f2
LEFT JOIN rabatt r ON r.fnrvon = f1.fnr AND r.fnran = f2.fnr
WHERE f1.fnr != f2.fnr
ORDER BY f1.fnr, f2.fnr;

SELECT fnrvon FROM rabatt UNION SELECT fnran FROM rabatt;