Use SOUNDEX() word by word on SQL Server

Question

Hi there,

Here is my problem. For example I have a table Products that contain a field Name:

Products
ID | Name | ..
1  | "USB Key 10Go"
2  | "Intel computer"
3  | "12 inches laptop computer"
...

I'm currently implementing a simple search engine (SQL Server and ASP .NET, C#) for an iPhone web-app and I would like to use the SOUNDEX() SQL Server function.

The thing is I can't directly use SOUNDEX on the Name field (this would be irrelevant since there are several words in the name), I would like to apply the SOUNDEX function to each word from the Name field, and then see if one of them match the researched keyword.

If someone have any clue how to do this, that would be awesome :)

Regards,

Charles

Answer 1

Rather than use Soundex you might be better off computing the Levenshtein distance between the two strings. See the Wikipedia article on Levenshtein distance.

There's a TSQL implementation of the Levenshtein distance algorithm here.

Share and enjoy.

Answer 2

Have you looked into the Full-Text Search feature in SQL Server? I know this is not exactly what you asked for. Its just that the SOUNDEX() function is used to find similar SOUNDING names (EX: SMITH and SMYTHE sound the same). In a search engine, however, how a word sounds is less important than the search words themselves. Full-Text Search also lets you use synonyms (allowing you to specify certain words that mean the same thing within your application's context), and have them automatically considered during your search.

Look at these pages for more information about Full Text Search in SQL Server:

Introduction to Full-Text Search

CONTAINS

CONTAINSTABLE

FREETEXT

FREETEXTTABLE

Answer 3

If you have to do it all in the RDBMS, a UDF would be the best if it's an option.

Otherwise, you could use this technique to at least soundex the first four words individually using PARSENAME:

From http://stackoverflow.com/questions/2647/split-string-in-sql/2685#2685:

PARSENAME(REPLACE('12 inches laptop computer', ' ', '.'), 1)  --return computer
PARSENAME(REPLACE('12 inches laptop computer', ' ', '.'), 2)  --return laptop
...

However: using PARSENAME in this way is a hack and a serious limitation is it only works for a max of 4 parts. If there are 5 or more words PARSENAME will return NULL, so you have to check for that with a conditional and degrade gracefully.

Here's a simplified example (again, without the NULL checks)

SELECT *
FROM Products 
WHERE SOUNDEX(search_input) = SOUNDEX(PARSENAME(REPLACE(Name, ' ', '.'), 4))
  OR SOUNDEX(search_input) = SOUNDEX(PARSENAME(REPLACE(Name, ' ', '.'), 3))
  OR SOUNDEX(search_input) = SOUNDEX(PARSENAME(REPLACE(Name, ' ', '.'), 2))
  OR SOUNDEX(search_input) = SOUNDEX(PARSENAME(REPLACE(Name, ' ', '.'), 1))

Answer 4

The SOUNDEX may be a perfect fit for your purpuse, but please remember that it may not provide good results for anything else than british or american english spoken words! It may even be used on german phonetical spoken words, but it will not work well with ANYTHING else.