﻿---
title: ES|QL multivalued fields
description: ES|QL can read from multivalued fields: Multivalued fields come back as a JSON array: The relative order of values in a multivalued field is undefined...
url: https://www.elastic.co/elastic/docs-builder/docs/2509/reference/query-languages/esql/esql-multivalued-fields
applies_to:
  - Elastic Cloud Serverless: Generally available
  - Elastic Stack: Generally available in 9.0+
---

# ES|QL multivalued fields
ES|QL can read from multivalued fields:

```json

{ "index" : {} }
{ "a": 1, "b": [2, 1] }
{ "index" : {} }
{ "a": 2, "b": 3 }


{
  "query": "FROM mv | LIMIT 2"
}
```

Multivalued fields come back as a JSON array:
```json
{
  "took": 28,
  "is_partial": false,
  "columns": [
    { "name": "a", "type": "long"},
    { "name": "b", "type": "long"}
  ],
  "values": [
    [1, [1, 2]],
    [2,      3]
  ]
}
```

The relative order of values in a multivalued field is undefined. They’ll frequently be in ascending order but don’t rely on that.

## Duplicate values

Some field types, like [`keyword`](/elastic/docs-builder/docs/2509/reference/elasticsearch/mapping-reference/keyword#keyword-field-type) remove duplicate values on write:

```json

{
  "mappings": {
    "properties": {
      "b": {"type": "keyword"}
    }
  }
}


{ "index" : {} }
{ "a": 1, "b": ["foo", "foo", "bar"] }
{ "index" : {} }
{ "a": 2, "b": ["bar", "bar"] }


{
  "query": "FROM mv | LIMIT 2"
}
```

And ES|QL sees that removal:
```json
{
  "took": 28,
  "is_partial": false,
  "columns": [
    { "name": "a", "type": "long"},
    { "name": "b", "type": "keyword"}
  ],
  "values": [
    [1, ["bar", "foo"]],
    [2,          "bar"]
  ]
}
```

But other types, like `long` don’t remove duplicates.

```json

{
  "mappings": {
    "properties": {
      "b": {"type": "long"}
    }
  }
}


{ "index" : {} }
{ "a": 1, "b": [2, 2, 1] }
{ "index" : {} }
{ "a": 2, "b": [1, 1] }


{
  "query": "FROM mv | LIMIT 2"
}
```

And ES|QL also sees that:
```json
{
  "took": 28,
  "is_partial": false,
  "columns": [
    { "name": "a", "type": "long"},
    { "name": "b", "type": "long"}
  ],
  "values": [
    [1, [1, 2, 2]],
    [2,    [1, 1]]
  ]
}
```

This is all at the storage layer. If you store duplicate `long`s and then convert them to strings the duplicates will stay:

```json

{
  "mappings": {
    "properties": {
      "b": {"type": "long"}
    }
  }
}


{ "index" : {} }
{ "a": 1, "b": [2, 2, 1] }
{ "index" : {} }
{ "a": 2, "b": [1, 1] }


{
  "query": "FROM mv | EVAL b=TO_STRING(b) | LIMIT 2"
}
```

```json
{
  "took": 28,
  "is_partial": false,
  "columns": [
    { "name": "a", "type": "long"},
    { "name": "b", "type": "keyword"}
  ],
  "values": [
    [1, ["1", "2", "2"]],
    [2,      ["1", "1"]]
  ]
}
```


## `null` in a list

`null` values in a list are not preserved at the storage layer:

```json

{ "a": [2, null, 1] }


{
  "query": "FROM mv | LIMIT 1"
}
```

```json
{
  "took": 28,
  "is_partial": false,
  "columns": [
    { "name": "a", "type": "long"}
  ],
  "values": [
    [[1, 2]]
  ]
}
```


## Functions

Unless otherwise documented functions will return `null` when applied to a multivalued field.

```json

{ "index" : {} }
{ "a": 1, "b": [2, 1] }
{ "index" : {} }
{ "a": 2, "b": 3 }
```

```json

{
  "query": "FROM mv | EVAL b + 2, a + b | LIMIT 4"
}
```

```json
{
  "took": 28,
  "is_partial": false,
  "columns": [
    { "name": "a",   "type": "long"},
    { "name": "b",   "type": "long"},
    { "name": "b + 2", "type": "long"},
    { "name": "a + b", "type": "long"}
  ],
  "values": [
    [1, [1, 2], null, null],
    [2,      3,    5,    5]
  ]
}
```

Work around this limitation by converting the field to single value with one of:
- [`MV_AVG`](/elastic/docs-builder/docs/2509/reference/query-languages/esql/functions-operators/mv-functions#esql-mv_avg)
- [`MV_CONCAT`](/elastic/docs-builder/docs/2509/reference/query-languages/esql/functions-operators/mv-functions#esql-mv_concat)
- [`MV_COUNT`](/elastic/docs-builder/docs/2509/reference/query-languages/esql/functions-operators/mv-functions#esql-mv_count)
- [`MV_MAX`](/elastic/docs-builder/docs/2509/reference/query-languages/esql/functions-operators/mv-functions#esql-mv_max)
- [`MV_MEDIAN`](/elastic/docs-builder/docs/2509/reference/query-languages/esql/functions-operators/mv-functions#esql-mv_median)
- [`MV_MIN`](/elastic/docs-builder/docs/2509/reference/query-languages/esql/functions-operators/mv-functions#esql-mv_min)
- [`MV_SUM`](/elastic/docs-builder/docs/2509/reference/query-languages/esql/functions-operators/mv-functions#esql-mv_sum)

```json

{
  "query": "FROM mv | EVAL b=MV_MIN(b) | EVAL b + 2, a + b | LIMIT 4"
}
```

```json
{
  "took": 28,
  "is_partial": false,
  "columns": [
    { "name": "a",   "type": "long"},
    { "name": "b",   "type": "long"},
    { "name": "b + 2", "type": "long"},
    { "name": "a + b", "type": "long"}
  ],
  "values": [
    [1, 1, 3, 2],
    [2, 3, 5, 5]
  ]
}
```