# \[] (element access)

[Read this page in HTML](https://www.scopedb.io/docs/reference/functions/semi-structured-data/get)

Reads an array element or an object field.

## Syntax

```scopeql
<data>[<index>]
<data>[<key>]
```

## Arguments

| Argument  | Type                        | Description                                                                                      |
| --------- | --------------------------- | ------------------------------------------------------------------------------------------------ |
| `<data>`  | `array`, `object`, or `any` | Value to read.                                                                                   |
| `<index>` | `int`                       | Array position, starting at 0. Negative indices count from the end; -1 selects the last element. |
| `<key>`   | `string`                    | Object key. An empty string is a valid key.                                                      |

## Returns

Returns `any`. Returns NULL when:

* The array index is out of range or the object key is missing.
* The input, index, or key is NULL.
* An `any` input has the wrong contained type: an integer index needs an array, and a string key needs an object.

## Examples

### Read nested event fields

Extract typed fields from a flexible payload, including the final item of a nested array.

```scopeql
VALUES ({
    'order': {'id': 'o-17', 'total_cents': 7900},
    'steps': ['cart_viewed', 'checkout_started', 'payment_completed']
})
SELECT $0 AS payload
SELECT
    payload['order']['id']::string AS order_id,
    payload['order']['total_cents']::int AS total_cents,
    payload['steps'][-1]::string AS last_step
```

```text
+----------+-------------+-------------------+
| order_id | total_cents | last_step         |
+----------+-------------+-------------------+
| o-17     | 7900        | payment_completed |
+----------+-------------+-------------------+
```

Cast extracted fields to the types needed by later expressions.

### Handle an optional event attribute

A coupon field can be present on one order and absent on another.

```scopeql
VALUES
    ('o-17', {'coupon': 'WELCOME'}), ('o-42', {'channel': 'web'})
SELECT $0 AS order_id, $1 AS payload
SELECT order_id, payload['coupon']::string AS coupon
```

```text
+----------+---------+
| order_id | coupon  |
+----------+---------+
| o-17     | WELCOME |
| o-42     | NULL    |
+----------+---------+
```