Azure IoT Hub device query language

The Azure IoT Hub can register thousands of devices. To manage them at scale, several kinds of tooling is made available.

First, using the Device Twin of each device, devices can store extra context (type, brand, vendor, version, location, features, etc.) using the Tags section.

In the Tags section of the device twin, you are free to add a number of (sub) nodes to this JSON document section:

The tags will never be readable by the device itself, these tags are used to query all devices in your IoT Hub and make subsets.

You, both as Azure portal user or as a programmer, can query all devices for specific features.

In the Azure portal, this ability to query is most visible when you open the list of (edge) devices:

This shows a new section where we can enter a SQL-ish query starting with “SELECT FROM devices WHERE”:

Let’s dive further into this query language.

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