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> Reference material for ARRAY_TRANSFORM function

# ARRAY_TRANSFORM

Returns an array by applying `<function>` on each element of `<array>`.

The Lambda function `<function>` is a mandatory parameter.

**Alias:** `TRANSFORM`

## Syntax

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
ARRAY_TRANSFORM(<function>, <array>)
```

## Parameters

| Parameter    | Description                                                                                                                    | Supported input type |
| :----------- | :----------------------------------------------------------------------------------------------------------------------------- | :------------------- |
| `<function>` | A [Lambda function](/guides/sql-dialect/arrays#manipulating-arrays-with-lambda-functions) used to check elements in the array. | Any Lambda function  |
| `<array>`    | The array to be transformed by the function.                                                                                   | Any array            |

## Return Type

`ARRAY` having the return type of `<function>` as its element type

## Examples

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT
	ARRAY_TRANSFORM(x -> x * 2, [ 1, 2, 3, 9 ] ) AS levels;
```

**Returns**: `[2, 4, 6, 18]`

In the example below, the `TRANSFORM` function is used to [CAST](/reference-sql/functions-reference/conditional-and-miscellaneous/cast) each element from a string to a date type. With each element now as a date type, the [INTERVAL](/reference-sql/lexical-structure/operators#arithmetic-with-date%2Ftime-and-intervals) function is then used to add 5 years to each.

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT
    ARRAY_TRANSFORM(x -> CAST(x as DATE) + INTERVAL '5 year',
        [ '1979-01-01', '1986-02-26', '1975-04-04' ] )
    AS registeredon;
```

**Returns**: `['1984-01-01 00:00:00'::TIMESTAMP, '1991-02-26 00:00:00'::TIMESTAMP, '1980-04-04 00:00:00'::TIMESTAMP]`

In the example below, `ARRAY_TRANSFORM` is used with `CASE` to modify specific elements based on a condition.

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT
    ARRAY_TRANSFORM(x, y -> CASE
        WHEN y = 'esimpson' THEN x
        ELSE 0
        END,
        [ 1, 2, 3 ],
        [ 'kennethpark', 'esimpson', 'sabrina21' ] )
    AS levels;
```

**Returns**: `[0, 2, 0]`

This example again uses `ARRAY_TRANSFORM` with `CASE`. Elements that don't meet the condition are left unchanged.

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT
    ARRAY_TRANSFORM(x, y -> CASE
        WHEN y % 2 == 0
        THEN UPPER(x)
        ELSE x END,
        [ 'esimpson', 'sabrina21', 'kennethpark' ],
        [ 1, 2, 3 ] )
    AS players;
```

**Returns**: `['esimpson', 'SABRINA21', 'kennethpark']`

This is another example using `CASE` that changes elements only if they meet the condition.

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT
    ARRAY_TRANSFORM(x, y -> CASE
        WHEN x < y THEN y
        ELSE x END,
        [ 100, 700, 800 ],
        [ 300, 500, 200 ] )
    AS res;
```

**Returns**: `[300, 700, 800]`