On Mon, 14 Nov 2005, Rhino wrote:
If you are asking whether MySQL already has a function that will calculate a
levenshtein-distance, I'm pretty sure that the answer is no. You can check
the MySQL manual yourself to be sure. The (English language manuals are at
http://dev.mysql.com/doc/ and other translations of the manuals can also be
accessed from that same page. You'll need to choose the appropriate manual
based on your version of MySQL; then look in the Functions and Operators
chapter.)
If you are asking whether MySQL supports user-defined functions (UDFs),
which allow you to add your own functions to MySQL, the answer is yes,
provided you are using Version 5 of MySQL. That means that if you can write
no v3 and v4 can too
the logic needed to calculate a levenshtein-distance in C or C++, you can
create your own UDF and add it to MySQL, then invoke it via the function
name in your SQL.
Possible problem: I see from your example that you want to put the function
in your ORDER BY clause; I'm not sure if you can do *that* in MySQL; I think
yes they can, but not efficient
... order by rand() ...
functions have to be invoked from the SELECT clause or HAVING clause or
maybe a few other places; I've never seen a function invoked in an ORDER BY
in either MySQL or DB2, which I know considerably better than MySQL. You may
want to try writing a trivial function and then seeing if you can invoke it
from an ORDER BY before you spend much time on the levenshtein-distance
function.... Of course, you could always rewrite your query so that the
function is invoked from the SELECT, like this:
select word1,word2, dist(word1, word2) from myTable order by 3
where the '3' in the ORDER BY clause indicates the third column of the
SELECT clause. That should be just as good as your original query.
Rhino
----- Original Message -----
From: "Horst Jäger" <[EMAIL PROTECTED]>
To: <mysql@lists.mysql.com>
Sent: Monday, November 14, 2005 11:02 AM
Subject: Let mysql calculate levenshtein-distance
Hi,
I have a nice little code snippet in pseudocode, which calculates the
levenshtein-distance between 2 words.
Is it possible to implement that code in mysql like in
"select word1,word2 from myTable order by dist(word1,word2 )"
where dist is the function mentionend above which takes 2 strings and
returns an int?
Weird question??? :)
Thanks
Horst
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