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> Reference material for JSON_POINTER_EXTRACT_KEYS function

# JSON_POINTER_EXTRACT_KEYS

Accepts a JSON document and pointer expression. If the key exists and holds a JSON object (map),
`JSON_POINTER_EXTRACT_KEYS` returns all the keys in that object as SQL `ARRAY(TEXT)`, removing outer quotes and decoding
characters. Otherwise, it returns `NULL`.

## Syntax

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
JSON_POINTER_EXTRACT_KEYS
(<json>, <json_pointer_expression>)
```

## Parameters

| Parameter                   | Description                                                                                                                                                                                                            | Supported input types |
| :-------------------------- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :-------------------- |
| `<json>`                    | The JSON document.                                                                                                                                                                                                     | `TEXT`                |
| `<json_pointer_expression>` | A JSON pointer expression to the location of the desired sub-document in the JSON. For more information, see [JSON pointer expression syntax](/reference-sql/functions-reference/json#json-pointer-expression-syntax). | `TEXT`                |

## Return Type

`ARRAY(TEXT)`

* If any input values are `NULL`, the function will return `NULL`.

## Examples

For the JSON document indicated by `<json_common_example>` below,
see [JSON common example](/reference-sql/functions-reference/json#json-common-example).

**Example**

The following code example extracts all the keys at path `/value` from the JSON document, removes the outermost quotes,
and returns the result as SQL `ARRAY(TEXT)`, labeled as `res`:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT JSON_POINTER_EXTRACT_KEYS(<json_common_example>, '/value') AS res
```

**Returns**

The previous code example returns the following:

| res (ARRAY(TEXT))                                      |
| :----------------------------------------------------- |
| `{'dyid', 'uid', 'keywords', 'tagIdToHits', 'events'}` |

**Example**

The following code example attempts to extract the keys at the path `/value/no_such_key` from the JSON document:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT JSON_POINTER_EXTRACT_KEYS(<json_common_example>, '/value/no_such_key') AS res
```

**Returns**

The previous code example returns the `NULL` with the result labeled as `res`, because the key does not exist:

| res (ARRAY(TEXT)) |
| :---------------- |
| NULL              |

**Example**

The following code example attempts to extract the value at the path `/value/keywords` from the JSON document:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT JSON_POINTER_EXTRACT_KEYS(<json_common_example>,'/value/keywords') AS res
```

**Returns**

The previous code example returns `NULL`, labeled as `res` because the value at the specified path is an array, not an
object:

| res (ARRAY(TEXT)) |
| :---------------- |
| NULL              |