Perform a right outer join

Use join.right() to perform an right outer join of two streams of data. Right joins output a row for each row in the right data stream with data matching from the left data stream. If there is no matching data in the left data stream, non-group-key columns with values from the left data stream are null.

Use join.right to join your data

1. Import the join package.

2. Define the left and right data streams to join:

   • Each stream must have one or more columns with common values. Column labels do not need to match, but column values do.
   • Each stream should have identical group keys.

   For more information, see join data requirements.

3. Use join.right() to join the two streams together. Provide the following required parameters:

   • left: Stream of data representing the left side of the join.
   • right: Stream of data representing the right side of the join.
   • on: Join predicate. For example: (l, r) => l.column == r.column.
   • as: Join output function that returns a record with values from each input stream. For example: (l, r) => ({r with column1: l.column1, column2: l.column2}).

The following example uses a filtered selection from the machineProduction sample data set as the left data stream and an ad-hoc table created with array.from() as the right data stream.

import "array"
import "influxdata/influxdb/sample"
import "join"

left =
    sample.data(set: "machineProduction")
        |> filter(fn: (r) => r.stationID == "g1" or r.stationID == "g2" or r.stationID == "g3")
        |> filter(fn: (r) => r._field == "oil_temp")
        |> last()

right =
    array.from(
        rows: [
            {station: "g1", opType: "auto", last_maintained: 2021-07-15T00:00:00Z},
            {station: "g2", opType: "manned", last_maintained: 2021-07-02T00:00:00Z},
        ],
    )

join.right(
    left: left |> group(),
    right: right,
    on: (l, r) => l.stationID == r.station,
    as: (l, r) => ({r with last_reported_val: l._value, last_reported_time: l._time}),
)