Special case of retrieving parent objects from children

Data Service
1

I have 2 tables:
Devices
Subscriptions
Subscriptions.device is a 1-to-1 relation with the Devices table.
I’ve had a little look over the documents and support forum but I can’t figure out if it’s possible to retrieve all Devices that are not a child of any Subscriptions, i.e. I require a list of Devices for which there are no Subscriptions that have a relationship with those Devices.

2

use this query for Devices table

Subscriptions[device].objectId is null
3

Ok, I see I have to use “is null”. I tried “Subscriptions[device].objectId == null” but got an ‘Invalid where clause’ error. Thanks!