mysql weighted random results - how to get changed variable value after SELECT - mysql

Question

I have a table keywords with columns keyword and weight. My goal is to randomly select one keyword, but to regard its weight (probability). I found two ways to solve this, where the latter one is more elegant (and consumes less ressources) - but i dont get it to run. See yourself.
The table and records:
CREATE TABLE IF NOT EXISTS `keywords` (
`keyword` varchar(100) COLLATE utf8_bin NOT NULL,
`weight` int(11) NOT NULL,
UNIQUE KEY `keywords` (`keyword`),
KEY `rate` (`weight`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
INSERT INTO `keywords` (`keyword`, `weight`) VALUES
('google', 50),
('microsoft', 20),
('apple', 10),
('yahoo', 5),
('bing', 5),
('xing', 5),
('cool', 5);
Query 1
Consumes more ressources, i work on 5k+ records. Source is Why would this MySQL query using rand() return no results about a third of the time?:
SELECT * FROM `keywords` ORDER BY -LOG(1.0 - RAND()) / weight LIMIT 1
Query 2
Sums up weights to #weight_sum. Sets #weight_point to RAND() number from within that range. Loops through all records, substracting weight from #weight_pos and setting #keyword to the current keywords.keyword. Until #weight_pos < 0. Then it keeps that keyword. Source is Random Weighted Choice in T-SQL
SET #keyword = 0;
SET #weight_sum = (SELECT SUM(weight) FROM keywords);
SET #rand = RAND();
SET #weight_point = ROUND(((#weight_sum - 1) * #rand + 1), 0);
SET #weight_pos = #weight_point;
SELECT
keyword,
weight,
#keyword:=CASE
WHEN #weight_pos < 0 THEN #keyword
ELSE keyword
END AS test,
(#weight_pos:=(#weight_pos - weight)) AS curr_weight,
#weight_point,
#keyword,
#weight_pos,
#rand,
#weight_sum
FROM
keywords;
See phpmyadmin results here http://postimg.org/image/stgpd776f/
My Question
How do i get the value in #keyword, or what the test column holds in the end? Adding a SELECT #keyword afterwards doesn't change anything.

Answer 1

Ok, i think my question was more or less a basic mysql-question. I achieved what i wanted by encapsulating the above SELECT statement into another SELECT, that then filtered the first one's result for what i searched. Sorry for bothering you. See the query:
SET #keyword = 0;
SET #weight_sum = (SELECT SUM(weight) FROM keywords);
SET #rand = RAND();
SET #weight_point = ROUND(((#weight_sum - 1) * #rand + 1), 0);
SET #weight_pos = #weight_point;
SELECT t.test FROM (
SELECT
keyword,
weight,
#keyword:=CASE
WHEN #weight_pos < 0 THEN #keyword
ELSE keyword
END AS test,
(#weight_pos:=(#weight_pos - weight)) AS curr_weight,
#weight_point,
##keyword,
#weight_pos,
#rand,
#weight_sum
FROM
keywords
) AS t
WHERE
t.curr_weight < 0
LIMIT
1;