Stai usando l'alias tabella in modo sbagliato. Non puoi eseguire UPDATE table1 t SET field1=val , devi scrivere UPDATE table1 SET field=val (Oppure UPDATE table1 SET field=val FROM table1 t ). Quindi cambia la tua query in
UPDATE [spdbprod.test.com\spprod].[aspnetdb].[dbo].[Communities_Groups]
SET Show = t2.show
FROM [spdbprod.test.com\spprod].[aspnetdb].[dbo].[Communities_Groups] t1
INNER JOIN [spdbQA.test.com\spQA].[aspnetdb].[dbo].
[Communities_Groups] t2 ON (t1.GroupID = t2.GroupID)
