You are building an Azure Analytics query that will receive input data from Azure IoT...

Box 1: LAG

The LAG analytic operator allows one to look up a “previous” event in an event stream, within certain constraints. It is very useful for computing the rate of growth of a variable, detecting when a variable crosses a threshold, or when a condition starts or stops being true.

Box 2: LIMIT DURATION

Example: Compute the rate of growth, per sensor:

SELECT sensorId,

growth = reading -

LAG(reading) OVER (PARTITION BY sensorId LIMIT DURATION(hour, 1))

FROM input