Hi!
I have four joins and it works very fast:
SELECT DISTINCTROW tblProAssociations.LogoLink,
tblProAssociations.$assoc_header
FROM (((tblExhibitions
LEFT JOIN jnExhibitions2Base ON (tblExhibitions.MainExhID = jnExhibitions2Base.ExhibitionID))
LEFT JOIN tblBaseExhibitions ON (jnExhibitions2Base.BaseExhibitionID = tblBaseExhibitions.MainExhID))
LEFT JOIN jnExhibitions2Assoc ON (tblBaseExhibitions.MainExhID = jnExhibitions2Assoc.BaseExhID))
LEFT JOIN tblProAssociations ON (jnExhibitions2Assoc.AssociationID = tblProAssociations.AssociationID)
WHERE $exh_condition AND tblProAssociations.LogoLink IS NOT NULL
ORDER BY tblProAssociations.$assoc_header;
Hope this helps,
Stas