---
title: experimental.unique() function
description: >
  `experimental.unique()` returns all records containing unique values in the `_value` column.
menu:
  flux_v0_ref:
    name: experimental.unique
    parent: experimental
    identifier: experimental/unique
weight: 101
flux/v0/tags: [transformations, selectors]
introduced: 0.112.0
---

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`experimental.unique()` returns all records containing unique values in the `_value` column.

`null` is considered a unique value.

#### Function behavior
- Outputs a single table for each input table.
- Outputs a single record for each unique value in an input table.
- Leaves group keys, columns, and values unmodified.
- Drops empty tables.

##### Function type signature

```js
(<-tables: stream[{A with _value: B}]) => stream[{A with _value: B}]
```

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

## Parameters

### tables

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




## Examples

### Return rows with unique values in each input table

```js
import "experimental"
import "sampledata"

sampledata.int(includeNull: true)
    |> experimental.unique()

```

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{{% expand "View example input and output" %}}

#### Input data

| _time                | _value  | *tag |
| -------------------- | ------- | ---- |
| 2021-01-01T00:00:00Z | -2      | t1   |
| 2021-01-01T00:00:10Z |         | t1   |
| 2021-01-01T00:00:20Z | 7       | t1   |
| 2021-01-01T00:00:30Z |         | t1   |
| 2021-01-01T00:00:40Z |         | t1   |
| 2021-01-01T00:00:50Z | 4       | t1   |

| _time                | _value  | *tag |
| -------------------- | ------- | ---- |
| 2021-01-01T00:00:00Z |         | t2   |
| 2021-01-01T00:00:10Z | 4       | t2   |
| 2021-01-01T00:00:20Z | -3      | t2   |
| 2021-01-01T00:00:30Z | 19      | t2   |
| 2021-01-01T00:00:40Z |         | t2   |
| 2021-01-01T00:00:50Z | 1       | t2   |


#### Output data

| _time                | _value  | *tag |
| -------------------- | ------- | ---- |
| 2021-01-01T00:00:00Z | -2      | t1   |
| 2021-01-01T00:00:10Z |         | t1   |
| 2021-01-01T00:00:20Z | 7       | t1   |
| 2021-01-01T00:00:50Z | 4       | t1   |

| _time                | _value  | *tag |
| -------------------- | ------- | ---- |
| 2021-01-01T00:00:00Z |         | t2   |
| 2021-01-01T00:00:10Z | 4       | t2   |
| 2021-01-01T00:00:20Z | -3      | t2   |
| 2021-01-01T00:00:30Z | 19      | t2   |
| 2021-01-01T00:00:50Z | 1       | t2   |

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