You can try following:
Create new report of appropriate type ("Current Status of Nodes, Interfaces, etc." for current UnDP data or "Historical-Custom Pollers" for historical data). Select Fields you are looking for. Now in Report menu select "Show SQL" and check the SQL query in SQL tab. The same steps can be used also for other tables if you are not sure about the tables, columns and the bindings.
The result for Custom node poller current status looks like:
CustomNodePollerStatus_CustomPollerStatus.Status AS Status, Nodes.NodeID AS NodeID
(Nodes INNER JOIN CustomPollerAssignment CustomNodePollerAssignment_CustomPollerAssignment ON (Nodes.NodeID = CustomNodePollerAssignment_CustomPollerAssignment.NodeID)) INNER JOIN CustomPollerStatus CustomNodePollerStatus_CustomPollerStatus ON (CustomNodePollerAssignment_CustomPollerAssignment.CustomPollerAssignmentID = CustomNodePollerStatus_CustomPollerStatus.CustomPollerAssignmentID)
(CustomNodePollerAssignment_CustomPollerAssignment.InterfaceID = 0)