Puoi creare una vista indicizzata basata sulla Relation
e Screen
tabelle e applicare lì un vincolo univoco.
create view DRI_UniqueScreens
with SCHEMABINDING
as
select r.AppId,s.Name
from
[Schema].Relation r
inner join
[Schema].Screen s
on
r.ScreenId = s.ScreenId
GO
CREATE UNIQUE CLUSTERED INDEX IX_DRI_UniqueScreens
on DRI_UniqueScreens (AppId,Name)