I have this table:
CREATE TABLE IF NOT EXISTS `catalog_sites` (
`id` int(10) unsigned NOT NULL auto_increment,
`cat_id` int(10) unsigned NOT NULL,
`date` datetime NOT NULL,
`url` varchar(255) NOT NULL,
`title` varchar(255) NOT NULL,
`description` varchar(255) NOT NULL,
`keywords` varchar(255) NOT NULL,
`visited` int(10) unsigned NOT NULL,
`shown` int(10) unsigned NOT NULL,
`meta_try` int(1) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `url` (`url`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
I think my problem is simple, but cant seem to find an appropriate solution..
So, this is a table with web-sites, I would like to get 6 sites in 6 different categories (cat_id, total: 36 rows) with the highest rating for each category. The rating is calculated as visited
/ shown
.
I should get 36 rows containing 6 top categories (we can find them by sorting with AVG(visited / shown)
), and 6 top sites in each of these 6 categories.
If you have any ideas how this might happen differently, please tell me.
I've tried your example, but it doesn't really work for me, or I just don't know how to adapt it to my case. Anyway, I'm still a noob as far as SQL goes, so I couldn't understand your query.
I have managed to solve my problem however. It's complicated and probably the worst possible approach. It is slow too, but I'll cache the results, so that shouldn't be a problem.
Here is my solution:
SET @site_limit = 2;
SET @cat_limit = 6;
SET @row = 0;
SET @limiter = 0;
SET @last_cat = 0;
SELECT `cat_id`, `url`, `visited` / `shown` AS `rating`, @limiter := IF(@last_cat = `cat_id`, IF(@limiter >= @site_limit - 1, @limiter, @limiter + 1), 0) AS `limiter`, @last_cat := `cat_id` AS `last_cat`
FROM `catalog_sites`
WHERE `cat_id`
IN (
SELECT `cat_id`
FROM (
SELECT `cat_id`, @row := @row + 1 AS `row`
FROM (
SELECT `cat_id`
FROM `catalog_sites`
GROUP BY `cat_id`
ORDER BY AVG(`visited` / `shown`) DESC
) AS derived1
) AS derived2
WHERE `row` <= @cat_limit
)
GROUP BY `cat_id`, `limiter`
ORDER BY `cat_id`, `rating` DESC