计算广告印象排名

这是一个很好的解决方案,它允许加权,它的coldfusion,但是sql也存在 article

DECLARE @girl TABLE (
id INT IDENTITY( 1, 1 ),
name VARCHAR( 50 ),
weight INT
);


INSERT INTO @girl
(
name,
weight
)(
SELECT 'Sarah', 100 UNION ALL
SELECT 'Libby', 30 UNION ALL
SELECT 'Lisa', 30 UNION ALL
SELECT 'Molly', 250 UNION ALL
SELECT 'Kit', 50
);

SELECT
g.id,
g.name,
g.weight
FROM
@girl g
INNER JOIN
(

--
--In this inner query, we need to select a random,
--weighted ID. We are doing this in the inner query
--rather than in the outter query so that our
--intermediary table doesn't need to contain so
--much information (just the ID).
--->
SELECT TOP 1
g.id
FROM
@girl g
INNER JOIN
pivot1000 p
ON
(
-- Use the weights. --->
g.weight >= p.id

--Use any additional filtering that is required by the business logic of the query criteria.

AND
g.name != 'Lisa'
)
ORDER BY
-- Select random row. --->
NEWID() ASC

) AS temp_id
ON
g.id = temp_id.id

一些相关问题可能也会有所帮助:

• Random Weighted Choice in T-SQL
• Random weighted choice

我们已经为我们的开源广告服务器AdServerBeans MyAds编写了一个MySQL函数( http://www.adserverbeans.com )在考虑流量共享的情况下随机选择横幅:

DELIMITER ;;
DROP FUNCTION if exists get_random_banner_by_traffic_share;
CREATE FUNCTION get_random_banner_by_traffic_share(valid_banners TEXT, total_traffic_share INTEGER)
RETURNS INTEGER
NOT DETERMINISTIC
BEGIN
       DECLARE pos INTEGER DEFAULT 1;
       DECLARE rnd INTEGER DEFAULT 0;
       DECLARE current_traffic_share INTEGER DEFAULT 0;
       DECLARE banner_id INTEGER;
       DECLARE banner_traffic_share INTEGER;
       SET rnd = RAND()*(total_traffic_share-1)+1;
       WHILE pos < LENGTH(valid_banners) DO       
         SET pos = POSITION(';' IN valid_banners);
         SET banner_id = CONVERT(SUBSTR(valid_banners,1,pos-1),SIGNED);
         SET valid_banners=SUBSTRING(valid_banners FROM pos+1);
         SET pos = POSITION(';' IN valid_banners);
         SET banner_traffic_share = CONVERT(SUBSTR(valid_banners,1,pos-1),SIGNED);
         SET valid_banners=SUBSTRING(valid_banners FROM pos+1);
         if(current_traffic_share < rnd and rnd <= (banner_traffic_share+current_traffic_share)) THEN
            RETURN banner_id;
         END IF;
         SET current_traffic_share=current_traffic_share+banner_traffic_share;
       END WHILE;
END;
;;
delimiter ;

MySQL存储过程/函数不支持数组/列表。所以我们必须使用带分隔符的字符串。 在此函数中,请注意以下行:

SET rnd = RAND()*(total_traffic_share-1)+1;

随机选择1到100之间的值。 那么我们就在那个范围内寻找旗帜。