docs-v2/content/flux/v0/stdlib/join/inner.md

title	description	menu	weight	flux/v0/tags	introduced
join.inner() function	`join.inner()` performs an inner join on two table streams.	flux_v0_ref name parent identifier join.inner join join/inner	101	transformations	0.172.0

join.inner() performs an inner join on two table streams.

The function calls join.tables() with the method parameter set to "inner".

Function type signature

(<-left: stream[A], as: (l: A, r: B) => C, on: (l: A, r: B) => bool, right: stream[B]) => stream[C] where A: Record, B: Record, C: Record

{{% caption %}} For more information, see Function type signatures. {{% /caption %}}

Parameters

left

Left input stream. Default is piped-forward data (<-).

right

({{< req >}}) Right input stream.

on

({{< req >}}) Function that takes a left and right record (l, and r respectively), and returns a boolean.

The body of the function must be a single boolean expression, consisting of one or more equality comparisons between a property of l and a property of r, each chained together by the and operator.

as

({{< req >}}) Function that takes a left and a right record (l and r respectively), and returns a record. The returned record is included in the final output.

Examples

Perform an inner join

import "sampledata"
import "join"

ints = sampledata.int()
strings = sampledata.string()

join.inner(
    left: ints,
    right: strings,
    on: (l, r) => l._time == r._time,
    as: (l, r) => ({l with label: r._value}),
)

{{< expand-wrapper >}} {{% expand "View example output" %}}

Output data

_time	_value	label	*tag
2021-01-01T00:00:00Z	-2	smpl_g9qczs	t1
2021-01-01T00:00:10Z	10	smpl_0mgv9n	t1
2021-01-01T00:00:20Z	7	smpl_phw664	t1
2021-01-01T00:00:30Z	17	smpl_guvzy4	t1
2021-01-01T00:00:40Z	15	smpl_5v3cce	t1
2021-01-01T00:00:50Z	4	smpl_s9fmgy	t1

_time	_value	label	*tag
2021-01-01T00:00:00Z	19	smpl_b5eida	t2
2021-01-01T00:00:10Z	4	smpl_eu4oxp	t2
2021-01-01T00:00:20Z	-3	smpl_5g7tz4	t2
2021-01-01T00:00:30Z	19	smpl_sox1ut	t2
2021-01-01T00:00:40Z	13	smpl_wfm757	t2
2021-01-01T00:00:50Z	1	smpl_dtn2bv	t2

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