ah, solved it with lots of unions... sometimes it helps to write it in text...

ill post the query in a sec, if someone else needs it.

UPDATE: here's the query.

SELECT id as carid, '1' as carparts FROM #cars WHERE part1=1

UNION

SELECT id as carid, '2' as carparts FROM #cars WHERE part2=1

UNION

SELECT id as carid, '3' as carparts FROM #cars WHERE part3=1