# FixedString

`FixedString(n)` stores exactly `n` bytes. Short input is padded with zero bytes; input longer than `n` bytes raises `STRING_TOO_LONG`.

Use this type when an external value has a fixed byte width. Use [String](https://coordinatordb.com/docs/reference/data-types/string) or `VARCHAR(n)` when the requirement is about text characters.

## Syntax

```text
FixedString(n)
```

* `n` — A positive byte length.

The size counts bytes, so a multibyte UTF-8 character can consume several positions. Padding is part of the value. Use `hex` to inspect it without embedding zero bytes in terminal output.

The length contract applies to casts, writes, defaults and generated values. A top-level column can contain SQL `NULL` unless declared `NOT NULL`.

## Examples

### Inspecting padding

```sql
SELECT hex(CAST('a' AS FixedString(3))) AS bytes,
       length(CAST('a' AS FixedString(3))) AS byte_count
FORMAT csv;
```

```text
"610000",3
```

### An input at the exact byte length

```sql
SELECT hex(CAST('abc' AS FixedString(3)))
FORMAT csv;
```

```text
"616263"
```

Casting `'abcd'` to `FixedString(3)` raises `STRING_TOO_LONG`.