# COUNTRY\_TO\_PHONE\_PREFIX

### Description

`COUNTRY_TO_PHONE_PREFIX` returns the international telephone calling code for a given ISO 3166-1 country code, as a string prefixed with `+`. Both alpha-2 (2-letter) and alpha-3 (3-letter) codes are accepted.

Returns `unknown` if the input is not a recognised country code.

### Syntax

```
COUNTRY_TO_PHONE_PREFIX(country_code)
```

**Returns:** A string such as `'+41'`, or `unknown` if the input is unrecognised.

### Example

```
COUNTRY_TO_PHONE_PREFIX('CH')
```

This returns `'+41'`.

```
COUNTRY_TO_PHONE_PREFIX('CHE')
```

This also returns `'+41'`.

```
COUNTRY_TO_PHONE_PREFIX('US')
```

This returns `'+1'`.

```
COUNTRY_TO_PHONE_PREFIX('XX')
```

This returns `unknown` — `'XX'` is not a valid ISO country code.

### Example in context

```
p is Person
CONCAT(COUNTRY_TO_PHONE_PREFIX(p.country), p.local_phone_number)
```

Combines the calling prefix for the person's country with their local number to produce a full international phone number, e.g. `'+41791234567'`.


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