Re: Probably a newbie question

I'd look here:

SELECT
name
FROM
vendor
WHERE
bom_item.vendor_key =
(
SELECT
vendor_key
FROM
mfg_vendor_relationship
WHERE
bom_item.mfg_key = mfg_key
AND
prefered = TRUE
AND
bom_item.project_key = project_key

)


-- 
Angular momentum makes the world go ‘round.

You might get away with adding

group by vendor_key

if it turns out you’re simply getting many copies of vendor key from that inner select.

Run it alone to see.