select lender_libelle as Propriétaire, location_libelle as Localisation, section_libelle as Section, count(*) as Nombre from exemplaires, lenders, docs_location, docs_section where expl_owner=idlender and idlocation=expl_location and idsection=expl_section group by lender_libelle,location_libelle,section_libelle order by 1,2,3