The soundex function converts a character string to a four-digit code for use in a comparison. It ignores vowels in the comparison. Nonalphabetic characters terminate the soundex evaluation. This function always returns some value. These two names have identical soundex codes:
select soundex ("smith"), soundex ("smythe")
----- ----- S530 S530
The difference function compares the soundex values of two strings and evaluates the similarity between them, returning a value from 0 to 4. A value of 4 is the best match. For example:
select difference("smithers", "smothers")
--------- 4 (1 row affected)
select difference("smothers", "brothers")
--------- 2 (1 row affected)
