---
title: keys() function
description: keys() returns the columns that are in the group key of each input table.
url: https://docs.influxdata.com/flux/v0/stdlib/universe/keys/
estimated_tokens: 2212
product: Flux
version: v0
publisher: InfluxData
canonical: https://docs.influxdata.com/flux/v0/stdlib/universe/keys/
date: '2024-04-08T16:01:02-06:00'
lastmod: '2024-04-08T16:01:02-06:00'
---

* Flux 0.13.0+

InfluxDB support

`keys()` returns the columns that are in the group key of each input table.

Each output table contains a row for each group key column label.
A single group key column label is stored in the specified `column` for each row.
All columns not in the group key are dropped.

##### Function type signature

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

For more information, see [Function type signatures](/flux/v0/function-type-signatures/).

## Parameters

### column

Column to store group key labels in. Default is `_value`.

### tables

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

## Examples

* [Return group key columns for each input table](#return-group-key-columns-for-each-input-table)
* [Return all distinct group key columns in a single table](#return-all-distinct-group-key-columns-in-a-single-table)
* [Return group key columns as an array](#return-group-key-columns-as-an-array)

### Return group key columns for each input table

```js
data
    |> keys()
```

[](#view-example-input-and-output)

View example input and output

#### Input data

|\*\_field|\*\_measurement|\*sensorID|       \_time       |\_value|
|---------|---------------|----------|--------------------|-------|
|   co    |  airSensors   | TLM0100  |2021-09-08T14:21:57Z| 0.31  |
|   co    |  airSensors   | TLM0100  |2021-09-08T14:22:07Z| 0.295 |
|   co    |  airSensors   | TLM0100  |2021-09-08T14:22:17Z| 0.314 |
|   co    |  airSensors   | TLM0100  |2021-09-08T14:22:27Z| 0.313 |

|\*\_field|\*\_measurement|\*sensorID|       \_time       |\_value|
|---------|---------------|----------|--------------------|-------|
|humidity |  airSensors   | TLM0100  |2021-09-08T14:21:57Z| 36.03 |
|humidity |  airSensors   | TLM0100  |2021-09-08T14:22:07Z| 36.07 |
|humidity |  airSensors   | TLM0100  |2021-09-08T14:22:17Z| 36.1  |
|humidity |  airSensors   | TLM0100  |2021-09-08T14:22:27Z| 36.12 |

| \*\_field |\*\_measurement|\*sensorID|       \_time       |\_value|
|-----------|---------------|----------|--------------------|-------|
|temperature|  airSensors   | TLM0100  |2021-09-08T14:21:57Z| 70.84 |
|temperature|  airSensors   | TLM0100  |2021-09-08T14:22:07Z| 70.86 |
|temperature|  airSensors   | TLM0100  |2021-09-08T14:22:17Z| 70.89 |
|temperature|  airSensors   | TLM0100  |2021-09-08T14:22:27Z| 70.85 |

#### Output data

|\*\_field|\*\_measurement|\*sensorID|   \_value   |
|---------|---------------|----------|-------------|
|   co    |  airSensors   | TLM0100  |   \_field   |
|   co    |  airSensors   | TLM0100  |\_measurement|
|   co    |  airSensors   | TLM0100  |  sensorID   |

|\*\_field|\*\_measurement|\*sensorID|   \_value   |
|---------|---------------|----------|-------------|
|humidity |  airSensors   | TLM0100  |   \_field   |
|humidity |  airSensors   | TLM0100  |\_measurement|
|humidity |  airSensors   | TLM0100  |  sensorID   |

| \*\_field |\*\_measurement|\*sensorID|   \_value   |
|-----------|---------------|----------|-------------|
|temperature|  airSensors   | TLM0100  |   \_field   |
|temperature|  airSensors   | TLM0100  |\_measurement|
|temperature|  airSensors   | TLM0100  |  sensorID   |

### Return all distinct group key columns in a single table

```js
data
    |> keys()
    |> keep(columns: ["_value"])
    |> distinct()
```

[](#view-example-input-and-output)

View example input and output

#### Input data

|\*\_field|\*\_measurement|\*sensorID|       \_time       |\_value|
|---------|---------------|----------|--------------------|-------|
|   co    |  airSensors   | TLM0100  |2021-09-08T14:21:57Z| 0.31  |
|   co    |  airSensors   | TLM0100  |2021-09-08T14:22:07Z| 0.295 |
|   co    |  airSensors   | TLM0100  |2021-09-08T14:22:17Z| 0.314 |
|   co    |  airSensors   | TLM0100  |2021-09-08T14:22:27Z| 0.313 |

|\*\_field|\*\_measurement|\*sensorID|       \_time       |\_value|
|---------|---------------|----------|--------------------|-------|
|humidity |  airSensors   | TLM0100  |2021-09-08T14:21:57Z| 36.03 |
|humidity |  airSensors   | TLM0100  |2021-09-08T14:22:07Z| 36.07 |
|humidity |  airSensors   | TLM0100  |2021-09-08T14:22:17Z| 36.1  |
|humidity |  airSensors   | TLM0100  |2021-09-08T14:22:27Z| 36.12 |

| \*\_field |\*\_measurement|\*sensorID|       \_time       |\_value|
|-----------|---------------|----------|--------------------|-------|
|temperature|  airSensors   | TLM0100  |2021-09-08T14:21:57Z| 70.84 |
|temperature|  airSensors   | TLM0100  |2021-09-08T14:22:07Z| 70.86 |
|temperature|  airSensors   | TLM0100  |2021-09-08T14:22:17Z| 70.89 |
|temperature|  airSensors   | TLM0100  |2021-09-08T14:22:27Z| 70.85 |

#### Output data

|   \_value   |
|-------------|
|   \_field   |
|\_measurement|
|  sensorID   |

### Return group key columns as an array

1. Use `keys()` to replace the `_value` column with the group key labels.
2. Use `findColumn()` to return the `_value` column as an array.

```
import "sampledata"

sampledata.int()
    |> keys()
    |> findColumn(fn: (key) => true, column: "_value")// Returns [tag]

```

#### Related

* [InfluxQL – SHOW MEASUREMENTS](/influxdb/v1/query_language/explore-schema/#show-measurements)
* [InfluxQL – SHOW FIELD KEYS](/influxdb/v1/query_language/explore-schema/#show-field-keys)
* [InfluxQL – SHOW TAG KEYS](/influxdb/v1/query_language/explore-schema/#show-tag-keys)
* [InfluxQL – SHOW SERIES](/influxdb/v1/query_language/explore-schema/#show-tag-keys)

[transformations](/flux/v0/tags/transformations/)
| *_field | *_measurement | *sensorID | _time | _value |
| --- | --- | --- | --- | --- |
| *_field | *_measurement | *sensorID | _time | _value |
| co | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 0.31 |
| co | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 0.295 |
| co | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 0.314 |
| co | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 0.313 |

| *_field | *_measurement | *sensorID | _time | _value |
| --- | --- | --- | --- | --- |
| *_field | *_measurement | *sensorID | _time | _value |
| humidity | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 36.03 |
| humidity | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 36.07 |
| humidity | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 36.1 |
| humidity | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 36.12 |

| *_field | *_measurement | *sensorID | _time | _value |
| --- | --- | --- | --- | --- |
| *_field | *_measurement | *sensorID | _time | _value |
| temperature | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 70.84 |
| temperature | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 70.86 |
| temperature | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 70.89 |
| temperature | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 70.85 |

| *_field | *_measurement | *sensorID | _value |
| --- | --- | --- | --- |
| *_field | *_measurement | *sensorID | _value |
| co | airSensors | TLM0100 | _field |
| co | airSensors | TLM0100 | _measurement |
| co | airSensors | TLM0100 | sensorID |

| *_field | *_measurement | *sensorID | _value |
| --- | --- | --- | --- |
| *_field | *_measurement | *sensorID | _value |
| humidity | airSensors | TLM0100 | _field |
| humidity | airSensors | TLM0100 | _measurement |
| humidity | airSensors | TLM0100 | sensorID |

| *_field | *_measurement | *sensorID | _value |
| --- | --- | --- | --- |
| *_field | *_measurement | *sensorID | _value |
| temperature | airSensors | TLM0100 | _field |
| temperature | airSensors | TLM0100 | _measurement |
| temperature | airSensors | TLM0100 | sensorID |

| *_field | *_measurement | *sensorID | _time | _value |
| --- | --- | --- | --- | --- |
| *_field | *_measurement | *sensorID | _time | _value |
| co | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 0.31 |
| co | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 0.295 |
| co | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 0.314 |
| co | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 0.313 |

| *_field | *_measurement | *sensorID | _time | _value |
| --- | --- | --- | --- | --- |
| *_field | *_measurement | *sensorID | _time | _value |
| humidity | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 36.03 |
| humidity | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 36.07 |
| humidity | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 36.1 |
| humidity | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 36.12 |

| *_field | *_measurement | *sensorID | _time | _value |
| --- | --- | --- | --- | --- |
| *_field | *_measurement | *sensorID | _time | _value |
| temperature | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 70.84 |
| temperature | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 70.86 |
| temperature | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 70.89 |
| temperature | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 70.85 |

| _value |
| --- |
| _value |
| _field |
| _measurement |
| sensorID |