# regexp\_replace

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Replaces all regular expression matches in a string.

## Syntax

```scopeql
regexp_replace(<string>, regex => <regex>, replacement => <replacement>)
```

## Arguments

| Argument      | Type     | Description                                                                                     |
| ------------- | -------- | ----------------------------------------------------------------------------------------------- |
| `<string>`    | `string` | String to transform.                                                                            |
| `regex`       | `string` | Constant. Regular expression. Must be valid and non-NULL.                                       |
| `replacement` | `string` | Constant. Replacement text. Use `$1` or `${name}` to refer to capture groups. Must not be NULL. |

## Returns

Returns `string`. If there is no match, returns the input unchanged. Returns NULL if the input is NULL.

## Examples

Replace numeric order IDs with a route placeholder so individual orders do not become separate groups.

```scopeql
VALUES ('/orders/17'), ('/orders/42'), ('/orders/42/refund')
SELECT $0 AS path
SELECT regexp_replace(path, regex => '/[0-9]+', replacement => '/:id') AS route
GROUP BY route
AGGREGATE count() AS requests
ORDER BY route
```

```text
+--------------------+----------+
| route              | requests |
+--------------------+----------+
| /orders/:id        | 2        |
| /orders/:id/refund | 1        |
+--------------------+----------+
```