---
title: columns() function
description: >
  `columns()` returns the column labels in each input table.
menu:
  flux_v0_ref:
    name: columns
    parent: universe
    identifier: universe/columns
weight: 101
flux/v0/tags: [transformations]
introduced: 0.14.0
---

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`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

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

{{% caption %}}
For more information, see [Function type signatures](/flux/v0/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

```js
import "sampledata"

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

```

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{{% 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 %}}
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