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 nonalphabetic characters in str are
ignored. All international alphabetic characters outside the A-Z range
are treated as vowels.
When using SOUNDEX(), you should be aware of the following limitations:
o 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 reliable results.
o This function is not guaranteed to provide consistent results with
strings that use multibyte character sets, including utf-8. See Bug
#22638 for more information.
mysql> SELECT SOUNDEX('Hello');
mysql> SELECT SOUNDEX('Quadratically');