You have 1,000 devices that connect to an Azure IoT hub.
You are performing a scheduled check of deployed IoT devices.
You plan to run the following command from the Azure CLI prompt. az iot hub query --hub-name hub1 --query-command "SELECT * FROM devices WHERE connectionState = 'Disconnected'"
What does the command return?
The command 'az iot hub query --hub-name hub1 --query-command "SELECT * FROM devices WHERE connectionState = 'Disconnected'"' returns the device twins of the devices where the connectionState is 'Disconnected'. Device twins are JSON documents that store metadata, configurations, and conditions. The query retrieves the relevant device twin data for the disconnected devices from the device registry in the IoT Hub.
seems like it should return the device twins of the disconnected devices
correct, confirmed here (see connectionState)> https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-identity-registry#device-heartbeat
should be device twins.
Yes. It should be Device twins. https://docs.microsoft.com/en-us/cli/azure/ext/azure-cli-iot-ext/iot/hub?view=azure-cli-latest#ext-azure-cli-iot-ext-az-iot-hub-query-examples
Review the section labeled Device and module twin queries, displaying arbitrary JSON objects, which IoT Hub enables you to query device twins and module twins. Such as; "connectionState" here is the article: https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-query-language#device-and-module-twin-queries
Device twins
Correct option is B. The command returns the Device twin of the disconnected devices.
Tried, returns data tiwns.
Indeed B...Tested with production data
It will be Device Twin only for the disconnected Device
the Device Disconnected events
Question says what does command return ? device twin is not something (telemetry or event or signal) which device return to hub. In my opinion A is correct.
Not disconnected devices The IoT Hub identity registry contains a field called connectionState. Only use the connectionState field during development and debugging. IoT solutions should not query the field at run time. For example, do not query the connectionState field to check if a device is connected before you send a cloud-to-device message or an SMS.
Device twin IoT Hub exposes the device twins as a document collection called devices. For example, the following query retrieves the whole set of device twins: SQL SELECT * FROM devices Source: https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-query-language