Probably a list of URI as returned by:
select URI from Interfaces
where Status = 0
and InterfaceIndex = -1
and NodeId = x
This is not much safe... Direct removal from DB by delete doesn't invoke consequential actions, so it will leave orphaned historical data, pollers, etc...
To delete the object you just need to know it's uri (e.g. as richard stated) and valid connection to SWISv.
Example for REST:
curl -X DELETE -H "Content-Type: application/json" -k -u admin: https://10.140.2.182:17778/SolarWinds/InformationService/v3/Json/swis:/qa-brn-jpel-02.swdev.local/Orion/Orion.Nodes/NodeID=1/Volumes/VolumeID=1
Other operations are described by Tim in SWIS REST/JSON API
I hope it helps.