Report of multiple different memberships per contact in one line
Please use the below SQL to list all the membership related to single membership in an single row - I guess this helps

select 
GROUP_CONCAT(b.name) 
from civicrm_membership a,civicrm_membership_type b where b.id = a.membership_type_id
and a.contact_id in (select contact_id from civicrm_membership GROUP BY contact_id having COUNT(*) > 1)