docs-v2/content/flux/v0.x/stdlib/universe/columns.md

title	description	menu	weight	flux/v0.x/tags	introduced
columns() function	`columns()` returns the column labels in each input table.	flux_0_x_ref name parent identifier columns universe universe/columns	101	transformations	0.14.0

columns() returns the column labels in each input table.

For each input table, columns outputs a table with the same group key columns and a new column containing the column labels in the input table. Each row in an output table contains the group key value and the label of one column of the input table. Each output table has the same number of rows as the number of columns of the input table.

Function type signature

(<-tables: stream[A], ?column: string) => stream[B] where A: Record, B: Record

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

Parameters

column

Name of the output column to store column labels in. Default is "_value".

tables

Input data. Default is piped-forward data (<-).

Examples

List all columns per input table

import "sampledata"

sampledata.string()
    |> columns(column: "labels")

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

Input data

_time	*tag	_value
2021-01-01T00:00:00Z	t1	smpl_g9qczs
2021-01-01T00:00:10Z	t1	smpl_0mgv9n
2021-01-01T00:00:20Z	t1	smpl_phw664
2021-01-01T00:00:30Z	t1	smpl_guvzy4
2021-01-01T00:00:40Z	t1	smpl_5v3cce
2021-01-01T00:00:50Z	t1	smpl_s9fmgy

_time	*tag	_value
2021-01-01T00:00:00Z	t2	smpl_b5eida
2021-01-01T00:00:10Z	t2	smpl_eu4oxp
2021-01-01T00:00:20Z	t2	smpl_5g7tz4
2021-01-01T00:00:30Z	t2	smpl_sox1ut
2021-01-01T00:00:40Z	t2	smpl_wfm757
2021-01-01T00:00:50Z	t2	smpl_dtn2bv

Output data

*tag	labels
t1	_time
t1	tag
t1	_value

*tag	labels
t2	_time
t2	tag
t2	_value

{{% /expand %}} {{< /expand-wrapper >}}