---
title: ES|QL MV_UNION function
description: 
url: https://www.elastic.co/elastic/docs-builder/docs/3016/reference/query-languages/esql/functions-operators/mv-functions/mv_union
products:
  - Elasticsearch
---

# ES|QL MV_UNION function
<applies-to>
  - Elastic Cloud Serverless: Preview
  - Elastic Stack: Planned
</applies-to>


## Syntax

![Embedded](https://www.elastic.co/elastic/docs-builder/docs/3016/reference/query-languages/esql/images/functions/mv_union.svg)


## Parameters

<definitions>
  <definition term="field1">
    Expression that can be null, a single value, or multiple values. Null values are treated as empty sets.
  </definition>
  <definition term="field2">
    Expression that can be null, a single value, or multiple values. Null values are treated as empty sets.
  </definition>
</definitions>


## Description

Returns all unique values from the combined input fields (set union). Null values are treated as empty sets; returns `null` only if both fields are null.

## Supported types


| field1          | field2          | result          |
|-----------------|-----------------|-----------------|
| boolean         | boolean         | boolean         |
| cartesian_point | cartesian_point | cartesian_point |
| cartesian_shape | cartesian_shape | cartesian_shape |
| date            | date            | date            |
| date_nanos      | date_nanos      | date_nanos      |
| double          | double          | double          |
| geo_point       | geo_point       | geo_point       |
| geo_shape       | geo_shape       | geo_shape       |
| geohash         | geohash         | geohash         |
| geohex          | geohex          | geohex          |
| geotile         | geotile         | geotile         |
| integer         | integer         | integer         |
| ip              | ip              | ip              |
| keyword         | keyword         | keyword         |
| keyword         | text            | keyword         |
| long            | long            | long            |
| text            | keyword         | keyword         |
| text            | text            | keyword         |
| unsigned_long   | unsigned_long   | unsigned_long   |
| version         | version         | version         |


## Examples

```esql
ROW a = [1, 2, 3, 4, 5], b = [2, 3, 4, 5, 6]
| EVAL finalValue = MV_UNION(a, b)
| KEEP finalValue
```


| finalValue:integer |
|--------------------|
| [1, 2, 3, 4, 5, 6] |

```esql
ROW a = [1, 2, 3, 4, 5]::long, b = [2, 3, 4, 5, 6]::long
| EVAL finalValue = MV_UNION(a, b)
| KEEP finalValue
```


| finalValue:long    |
|--------------------|
| [1, 2, 3, 4, 5, 6] |

```esql
ROW a = [true, false], b = [false]
| EVAL finalValue = MV_UNION(a, b)
| KEEP finalValue
```


| finalValue:boolean |
|--------------------|
| [true, false]      |

```esql
ROW a = [5.2, 10.5, 1.12345], b = [10.5, 2.6928]
| EVAL finalValue = MV_UNION(a, b)
| KEEP finalValue
```


| finalValue:double            |
|------------------------------|
| [5.2, 10.5, 1.12345, 2.6928] |

```esql
ROW a = ["one", "two", "three"], b = ["two", "four"]
| EVAL finalValue = MV_UNION(a, b)
| KEEP finalValue
```


| finalValue:keyword              |
|---------------------------------|
| ["one", "two", "three", "four"] |