---
title: duplicate() function
description: >
  `duplicate()` duplicates a specified column in a table.
menu:
  flux_v0_ref:
    name: duplicate
    parent: universe
    identifier: universe/duplicate
weight: 101
flux/v0/tags: [transformations]
introduced: 0.7.0
---

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`duplicate()` duplicates a specified column in a table.

If the specified column is part of the group key, it will be duplicated, but
the duplicate column will not be part of the output’s group key.

##### Function type signature

```js
(<-tables: stream[A], as: string, 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
({{< req >}})
Column to duplicate.



### as
({{< req >}})
Name to assign to the duplicate column.

If the `as` column already exists, it will be overwritten by the duplicated column.

### tables

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




## Examples

### Duplicate a column

```js
import "sampledata"

sampledata.int()
    |> duplicate(column: "tag", as: "tag_dup")

```

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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 | 10      | t1   |
| 2021-01-01T00:00:20Z | 7       | t1   |
| 2021-01-01T00:00:30Z | 17      | t1   |
| 2021-01-01T00:00:40Z | 15      | t1   |
| 2021-01-01T00:00:50Z | 4       | t1   |

| _time                | _value  | *tag |
| -------------------- | ------- | ---- |
| 2021-01-01T00:00:00Z | 19      | 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 | 13      | t2   |
| 2021-01-01T00:00:50Z | 1       | t2   |


#### Output data

| _time                | _value  | *tag | tag_dup  |
| -------------------- | ------- | ---- | -------- |
| 2021-01-01T00:00:00Z | -2      | t1   | t1       |
| 2021-01-01T00:00:10Z | 10      | t1   | t1       |
| 2021-01-01T00:00:20Z | 7       | t1   | t1       |
| 2021-01-01T00:00:30Z | 17      | t1   | t1       |
| 2021-01-01T00:00:40Z | 15      | t1   | t1       |
| 2021-01-01T00:00:50Z | 4       | t1   | t1       |

| _time                | _value  | *tag | tag_dup  |
| -------------------- | ------- | ---- | -------- |
| 2021-01-01T00:00:00Z | 19      | t2   | t2       |
| 2021-01-01T00:00:10Z | 4       | t2   | t2       |
| 2021-01-01T00:00:20Z | -3      | t2   | t2       |
| 2021-01-01T00:00:30Z | 19      | t2   | t2       |
| 2021-01-01T00:00:40Z | 13      | t2   | t2       |
| 2021-01-01T00:00:50Z | 1       | t2   | t2       |

{{% /expand %}}
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