Beginning SQL

Chapter 5
176
FirstName SOUNDEX(FirstName)
John J500
Jamie J500
Catherine C365
Steve S310
William W450
Stuart S363
Seymour S560
Note that you may get slightly difference results because different database systems implement slightly
different versions of the SOUNDEX() algorithm.
Admittedly, the results are perhaps not that useful without an in-depth understanding of SOUNDEX()
and the algorithm, whose rules are fairly complex. You can learn all about the SOUNDEX() system at
www.archives.gov/research_room/genealogy/census/soundex.html.
However, the good news is that the DIFFERENCE() function interprets SOUNDEX() values and returns a
number between 0 and 4 comparing how two strings sound. The more similar they sound, the higher the
number. DIFFERENCE() takes two arguments: the two strings to be compared. The DIFFERENCE() function’s
syntax is as follows:
DIFFERENCE(some_name, comparison_name)
Note that Oracle, MySQL, and MS Access don’t support the DIFFERENCE() function.
Say, for example, that you want the details of all members whose first name sounds like Katherine or
Johnny. You could use the DIFFERENCE() function to help you find those details. The following is a SQL
statement that returns the difference value for Katherine and Johnny compared to values from the
FirstName column:
SELECT FirstName,DIFFERENCE(FirstName, ‘Katherine’),
DIFFERENCE(FirstName, ‘Johnny’)
FROM MemberDetails;
The query results are shown in the following table:
FirstName DIFFERENCE(FirstName, ‘Katherine’) DIFFERENCE(FirstName, ‘Johnny’)
Katie 2 2
Susie 0 2
Doris 1 1
Jenny 1 4