SOUNDEX function in SQL

The purpose of the DIFFERENCE function is to find out how close the SOUNDEX values for two string expressions are to each other.

The value returned by the DIFFERENCE function ranges from 0 to 4 and represents the number of characters in the SOUNDEX values which are the same (this can't be more than 4).

So, the larger the number returned by the DIFFERENCE function the closer the string expressions sound to each other i.e. 4 means they're very similar and 0 means there's little or no similarity.