parse nested Json string in Azure Stream Analytics

Tran, Hoa 26 Reputation points

Input data is streaming every 6s - the json array is below

"value": "{\"vrms\":0,\"apeak\":-102.4}",
"EventProcessedUtcTime": "2022-03-28T16:37:59.6289183Z",
"PartitionId": 0,
"EventEnqueuedUtcTime": "2022-03-28T15:37:58.0930000Z",
"IoTHub": {
"MessageId": "MSG_ID",
"CorrelationId": "CORE_ID",
"ConnectionDeviceId": "RUT955",
"ConnectionDeviceGenerationId": "637829563755785214",
"EnqueuedTime": "2022-03-28T15:37:58.0000000Z"

I'm trying to access the vrms and apeak value in the input data. I'm using the query below:


However, I keep getting the error
StepSplitter should never put Updatable UDFs and ML callouts in the same step! Step name powerbivisuoutputs0

My parseJson function is

function main(x) {
return JSON.parse(x);

Azure Stream Analytics
Azure Stream Analytics
An Azure real-time analytics service designed for mission-critical workloads.
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Accepted answer
  1. HimanshuSinha-msft 19,246 Reputation points Microsoft Employee

    Hello @Tran, Hoa ,
    Thanks for the question and using MS Q&A platform.

    As we understand the ask here is know how to use the JSON.parse , please do let us know if its not accurate.
    Just to let know that the JSON.parse function is to be used to query Azure SQL data streams .
    Azure SQL Database as reference data in your job, it's possible to have a column that has data in JSON format. An example is shown below.

    I did went ahead and looked into the JSON which you shared

    "value": "{\"vrms\":0,\"apeak\":-102.4}"

    If we try to query this , we get

    Select value.vrms from Input


    If ths json is updated to

    "value": {"vrms":0,"apeak":-102.4}

    Select value.vrms,value.apeak from Input


    Please do let me if you have any queries.

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