> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/reference/sql-functions/string-functions/soundex.md).

# SOUNDEX

## Syntax

```bnf
SOUNDEX(str)
```

## Description

Returns a soundex string from *`str`*. Two strings that sound almost the same should have identical soundex strings. A standard soundex string is four characters long, but the `SOUNDEX()` function returns an arbitrarily long string. You can use `SUBSTRING()` on the result to get a standard soundex string. All non-alphabetic characters in *`str`* are ignored. All international alphabetic characters outside the A-Z range are treated as vowels.

**Important:** When using `SOUNDEX()`, you should be aware of the following details:

* This function, as currently implemented, is intended to work well with strings that are in the English language only. Strings in other languages may not produce reasonable results.
* This function implements the original Soundex algorithm, not the more popular enhanced version (also described by D. Knuth). The difference is that original version discards vowels first and duplicates second, whereas the enhanced version discards duplicates first and vowels second.

## Examples

```sql
SOUNDEX('Hello');
+------------------+
| SOUNDEX('Hello') |
+------------------+
| H400             |
+------------------+
```

```sql
SELECT SOUNDEX('MariaDB');
+--------------------+
| SOUNDEX('MariaDB') |
+--------------------+
| M631               |
+--------------------+
```

```sql
SELECT SOUNDEX('Knowledgebase');
+--------------------------+
| SOUNDEX('Knowledgebase') |
+--------------------------+
| K543212                  |
+--------------------------+
```

```sql
SELECT givenname, surname FROM users WHERE SOUNDEX(givenname) = SOUNDEX("robert");
+-----------+---------+
| givenname | surname |
+-----------+---------+
| Roberto   | Castro  |
+-----------+---------+
```

## See Also

* [SOUNDS LIKE](/docs/server/reference/sql-functions/string-functions/sounds-like.md)()

<sub>*This page is licensed: GPLv2, originally from*</sub> [<sub>*fill\_help\_tables.sql*</sub>](https://github.com/MariaDB/server/blob/main/scripts/fill_help_tables.sql)

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