How can i query a map field in ksql?

Question

I have created a stream from a topic i ksql. The stream has the fields as below. I can query diferent field for example: select category from fake-data-119 . I would like to know how can i get a single item from the map field, for example : status?

The data that are coming from the source are:

ProducerRecord(topic=fake-data-119, partition=null, headers=RecordHeaders(headers = [], isReadOnly = true), key=null, value={"deviceId": 16, "category": "visibility sensors", "timeStamp": "Tue Jun 19 10:11:10 CEST 2018", "deviceProperties": {"visibility": "72", "status": "true"}}, timestamp=null)
ProducerRecord(topic=fake-data-119, partition=null, headers=RecordHeaders(headers = [], isReadOnly = true), key=null, value={"deviceId": 6, "category": "fans", "timeStamp": "Tue Jun 19 10:11:11 CEST 2018", "deviceProperties": {"temperature": "22", "rotationSense": "1", "status": "false", "frequency": "56"}}, timestamp=null)
ProducerRecord(topic=fake-data-119, partition=null, headers=RecordHeaders(headers = [], isReadOnly = true), key=null, value={"deviceId": 23, "category": "air quality monitors", "timeStamp": "Tue Jun 19 10:11:12 CEST 2018", "deviceProperties": {"coPpm": "136", "status": "false", "Co2Ppm": "450"}}, timestamp=null)

I am using the statement below to create the stream:

CREATE STREAM fakeData119 WITH (KAFKA_TOPIC='fake-data-119', VALUE_FORMAT='AVRO');

  Field            | Type                                 
    ---------------------------------------------------------
     ROWTIME          | BIGINT           (system)            
     ROWKEY           | VARCHAR(STRING)  (system)            
     DEVICEID         | INTEGER                              
     CATEGORY         | VARCHAR(STRING)                      
     TIMESTAMP        | VARCHAR(STRING)                      
     DEVICEPROPERTIES | MAP[VARCHAR(STRING),VARCHAR(STRING)] 
    ---------------------------------------------------------
    ksql> select * from fakeData119;
    1529394182864 | null | 6 | fans | Tue Jun 19 09:43:02 CEST 2018 | {temperature=36, rotationSense=1, status=false, frequency=72}
    1529394183869 | null | 5 | fans | Tue Jun 19 09:43:03 CEST 2018 | {temperature=23, rotationSense=1, status=true, frequency=76}
    1529394184872 | null | 16 | visibility sensors | Tue Jun 19 09:43:04 CEST 2018 | {visibility=14, status=true}
    1529394185875 | null | 25 | air quality monitors | Tue Jun 19 09:43:05 CEST 2018 | {coPpm=280, status=false, Co2Ppm=170}

Answer 1

您可以通过以下方式获取地图中的项目：

select deviceproperties['status'] from fakedata119