For full details, please see

https://www.windows-noob.com/forums/index.php?/topic/7308-collection-membership/#entry27677

select 
    C.Name
from 
    dbo.v_FullCollectionMembership FCM
    join dbo.v_Collection C on C.CollectionID = FCM.CollectionID
Where
    FCM.Name = 'Gartek-DC'