SELECT 
defName AS Prozess, 
SUM(lCount) AS Schleifendurchläufe 
 FROM 
  (
    SELECT vi.definitionname AS defName, vi."name" AS instName, va."LOOPCOUNT" AS lCount, vi.id AS piId
    FROM view_instance vi, view_activity va
    WHERE va."LOOPCOUNT" IS NOT NULL 
    AND va."INSTANCEID" = vi.id
  GROUP BY vi.id, vi.definitionname, vi."name",va."LOOPCOUNT") 
  GROUP BY defName​