Optimize Sorting for Soundex Search Results in Microsoft SQL Server

Provided by Jim Ferguson, Project Manager

Soundex Function

The Microsoft SQL Server Soundex function is used to find similar strings based on a search pattern and ideal when there are small typos that result in duplicate values. The Soundex function calculates a numerical value for a string.

For more information on the Soundex function in SQL Server, visit Microsoft's SQL Server Developer Center.

Problem

It's a bit tricky to sort the results of all the records with the same Soundex value. Sorting on the original field just puts them in alphabetical order rather than by closeness to the desired value.

Solution

Fortunately, there's a simple way to display the exact and partially-matching strings first in the search results. Use a sort expression to ensure that exact and partial matches sort to the top of the list before other matching strings.

In this example, we're showing the names with a Soundex value of "knapp'. The display sorts all the 'knapp' values first, then those that start with 'knapp', and finally the other records with spellings that result in the same Soundex value as 'knapp':

select lastname 
from Customers 
where soundex(lastname) = soundex('knapp')
order by
case when lastname like'knapp%'
then 0
else 1
end,
lastname

The result is a list that shows the exact matches, those that start with the original letters, and the remaining "close" ones.