Notify when current changes

In IoT scenarios, it is a very common scenario to trigger events when indicators change. This article will use current changes as an example to introduce eKuiper SQL rules.

background

In this scenario, stream will continuously send the current current data in the form of a stream, as well as the timestamp to which the data belongs. eKuiper rules will accept this data flow and meet the requirements with the defined rules, the data is as follows:

{"current":200,"ts":1}
{"current":400,"ts":2}
{"current":300,"ts":3}
{"current":200,"ts":4}

The current changes from less than 300A to more than 300A

select current, ts from demo where current > 300 and lag(current) < 300;

This rule will record the last data of the current, and then compare it with the current data. Once the conditions are met, the event will be triggered.

{"current":200,"ts":1}
{"current":400,"ts":2} output event
{"current":300,"ts":3}
{"current":200,"ts":4}

The total current exceeds 200A for 10 seconds

select current from demo group by SLIDINGWINDOW(ss,0,10) over (when current > 200) having min(current) > 200;

This rule will open a window when receiving current data above 200A. If the smallest data in the window is also greater than 200A, the requirements are met and the event is output.

{"current":100,"ts":1}
{"current":300,"ts":2}
{"current":300,"ts":3}
{"current":300,"ts":4}
{"current":300,"ts":5}
{"current":300,"ts":6}
{"current":300,"ts":7}
{"current":300,"ts":8}
{"current":300,"ts":9}
{"current":300,"ts":10}
{"current":300,"ts":11} output event