MySQL SOUNDEX is one of the String functions, which is to return the Soundex code of a given string. Generally, it returns the four digits’ standard code as an output. However, this is not the case for the long-string arguments.
As the name suggests, the SOUNDEX returns the code based on the string sound. I mean, if two strings sound identical, then the value will be identical too. The basic syntax of the MySQL SOUNDEX Function is as shown below:
SELECT SOUNDEX(String_Expression) FROM [Source]
MySQL SOUNDEX Function Example
It returns the Soundex code value of a user-specified string expression. The following query shows you multiple ways to use this function.
SELECT SOUNDEX('Hello');
SELECT SOUNDEX('MySQL');
SELECT SOUNDEX('Suresh');

Let me show you another MySQL example for better understanding. Within the last statement, we used a NULL value. Remember, this String method returns NULL for NULL argument value.
SELECT SOUNDEX('Hi');
SELECT SOUNDEX('Hello');
SELECT SOUNDEX(NULL);
