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Stream Join

Provides examples on joining two stream based on a condition.

For more information on other join operations refer the Siddhi query guide.

define stream TemperatureStream
        (roomNo string, temperature double);

define stream HumidityStream
        (roomNo string, humidity double);

@info(name = 'Equi-join')
from TemperatureStream#window.unique:time(roomNo, 1 min) as t
    join HumidityStream#window.unique:time(roomNo, 1 min) as h
    on t.roomNo == h.roomNo
select t.roomNo, t.temperature, h.humidity
insert into TemperatureHumidityStream;

@info(name = 'Join-on-temperature')
from TemperatureStream as t
    left outer join HumidityStream#window.time(1 min) as h
    on t.roomNo == h.roomNo
select t.roomNo, t.temperature, h.humidity
insert into EnrichedTemperatureStream;

define stream TemperatureStream (roomNo string, temperature double);
define stream HumidityStream (roomNo string, humidity double);
@info(name = 'Equi-join')
from TemperatureStream#window.unique:time(roomNo, 1 min) as t join HumidityStream#window.unique:time(roomNo, 1 min) as h on t.roomNo == h.roomNo	Join latest temperature and humidity events arriving within 1 minute for each roomNo.
select t.roomNo, t.temperature, h.humidity insert into TemperatureHumidityStream;
@info(name = 'Join-on-temperature')
from TemperatureStream as t	Join when events arrive in TemperatureStream.
left outer join HumidityStream#window.time(1 min) as h on t.roomNo == h.roomNo	When events get matched in time() window, all matched events are emitted, else null is emitted.
select t.roomNo, t.temperature, h.humidity insert into EnrichedTemperatureStream;

Join Behavior

When events are sent to TemperatureStream stream and HumidityStream stream, following events will get emitted at TemperatureHumidityStream stream via Equi-join query, and EnrichedTemperatureStream stream via Join-on-temperature query.

Time	Input to TemperatureStream	Input to HumidityStream	Output at TemperatureHumidityStream	Output at EnrichedTemperatureStream
9:00:00	['1001', 18.0]	-	-	['1001', 18.0, null]
9:00:10	-	['1002', 72.0]	-	-
9:00:15	-	['1002', 73.0]	-	-
9:00:30	['1002', 22.0]	-	['1002', 22.0, 73.0]	['1002', 22.0, 72.0], ['1002', 22.0, 73.0]
9:00:50	-	['1001', 60.0]	['1001', 18.0, 60.0]	-
9:01:10	-	['1001', 62.0]	-	-
9:01:20	['1001', 17.0]	-	['1001', 17.0, 62.0]	['1001', 17.0, 60.0], ['1001', 17.0, 62.0]
9:02:10	['1002', 23.5]	-	-	['1002', 23.5, null]

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