How to set a variable if a row already exists?

[djeyewater]

I have a table like so:

CREATE TABLE `shortURL` (
 `id` int(10) UNSIGNED NOT NULL AUTO_INCREMENT,
 `sURL` varchar(5) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
 `lURL` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
 PRIMARY KEY (`id`),
 UNIQUE KEY `lURL` (`lURL`),
 KEY `sURL` (`sURL`)
) ENGINE=InnoDB AUTO_INCREMENT=15 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci

What I want to do is to try inserting a new row with a value into the lURL field, but if the record already exists, then set a variable @sURL to the value of the sURL column for the record in question.

Currently I'm doing this like so:

INSERT INTO shortURL VALUES(NULL, '', lURL)
        #If the long URL already exists, then set @sURL to the short URL value
        ON DUPLICATE KEY UPDATE
        id = IF( (@sURL := sURL), id, id);

Is there a better way of setting the @sURL to the value of sURL if the record already exists?

The full procedure looks like this:

CREATE FUNCTION makesURL (lURL CHAR(255))
RETURNS CHAR(5) DETERMINISTIC
BEGIN
    #First try and insert the long URL
    INSERT INTO shortURL VALUES(NULL, '', lURL)
        #If the long URL already exists, then set @sURL to the short URL value
        ON DUPLICATE KEY UPDATE
        id = IF( (@sURL := sURL), id, id);
    #If the record didn't already exist, so we've just inserted a new record, create the short URL and update the record
    IF @sURL IS NULL THEN
        SET @sURL = strFromNum(LAST_INSERT_ID());
        UPDATE shortURL SET shortURL.sURL = @sURL
            WHERE shortURL.id = LAST_INSERT_ID()
            LIMIT 1;
    END IF;
    RETURN @sURL;
END//

P.S. Most records will be new, so trying to insert the record first rather than trying to select it first is much faster.

Thanks

Dave