This would do the trick for the trigger:
JOIN ContainerMemberSnapshots ON Containers_AlertsAndReportsData.GroupMemberSnapshotID = ContainerMemberSnapshots.ContainerMemberSnapshotID
JOIN Nodes ON ContainerMemberSnapshots.EntityID = Nodes.NodeID
WHERE Nodes.DateAdded > DateAdd(dd, -30, GetDate())
And this would work for the reset:
JOIN ContainerMemberSnapshots ON Containers_AlertsAndReportsData.GroupMemberSnapshotID = ContainerMemberSnapshots.ContainerMemberSnapshotID
JOIN Nodes ON ContainerMemberSnapshots.EntityID = Nodes.NodeID
WHERE Nodes.DateAdded <= DateAdd(dd, -30, GetDate())
