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> Reference material for ARRAY_CONCAT function

# ARRAY_CONCAT

**Alias:** `ARRAY_CAT`

Combines one or more arrays that are passed as arguments.

## Syntax

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
ARRAY_CONCAT(<array> [, ...n])
```

**—OR—**

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
<expression> || <expression>
```

## Parameters

| Parameter          | Description                                                                            | Supported input types |
| :----------------- | :------------------------------------------------------------------------------------- | :-------------------- |
| `<array> [, ...n]` | The arrays to be combined. If only one array is given, an identical array is returned. | `ARRAY`               |

### `||` operator

| Parameter      | Description                         | Supported input types                      |
| :------------- | :---------------------------------- | :----------------------------------------- |
| `<expression>` | The expressions to be concatenated. | `TEXT` / `ARRAY`, but at least one `ARRAY` |

To enable array concatenation, one parameter to the `||` operator must be of type `ARRAY`, while the other parameter can be a string whose value can be converted to the underlying type of the array parameter, or it can be an array of the same type.

If one parameter to the `||` operator is `NULL`, the result will be the non-null parameter; if both parameters are `NULL`, the result will be `NULL`.

The concatenation operator `||` can also be used for [string concatenation](/reference-sql/functions-reference/string/concat).

## Return Type

`ARRAY` of the same type as the input arrays

## Example

In the following example, two arrays are combined to show all of the levels in a particular game:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT
    ARRAY_CONCAT([ 1, 2, 3, 4 ], [ 5, 6, 7, 8, 9, 10 ]) AS levels;
```

**Returns**: `[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]`

The following example concatenates two integer arrays:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT ARRAY[1,2] || ARRAY[3];
```

**Returns**: `[1, 2, 3]`

The following example concatenates a string, whose value can be converted to integer, with an integer array:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT '{2}' || ARRAY[1];
```

**Returns**: `[2, 1]`