Is there any algorithm to make some ad display at random more often than others

Databases
1

Hi,
I have a table of advertisement with expiry date and location. Currently, I display ad at random base on user’s location.

In the near future, I want to add tier system in to my ad sale. It means the first tier ad should be displayed more often than the second tier, but I don’t know how to control that.

Is there any existing solution for my problem?

Thank you,

2

Anyone? Here’s the code I’ve been done so far:
Creating a table:


$mysqli->query("CREATE TABLE `ads` (
  `id` INT NOT NULL AUTO_INCREMENT,
  `uid` INT NOT NULL,
  `txt` TEXT NOT NULL,
  `date` DATE NOT NULL default '0000-00-00',
  `img` VARCHAR( 120 ) NOT NULL,
  `location` VARCHAR( 75 ) NOT NULL,
  `expiry` DATE NOT NULL default '0000-00-00',
PRIMARY KEY ( `id` ),
UNIQUE (
  `id`
  )
) ENGINE = INNODB CHARACTER SET UTF8 COLLATE utf8_general_ci
")
or die("DB error!");

Random with PHP:


SELECT id, uid, img, location, expiry
FROM ads
WHERE location = '$location' AND CURDATE() < expiry AND RAND()<(SELECT ((1/COUNT(*))*10) FROM ads)
ORDER BY RAND()
LIMIT 1

Some one suggests I have to add some sort of percentage but I wasn’t lucky with Google search.

3

similar thread on (shock!) another forum yesterday…

4

Thank you. Any added knowledge is good news. I’m now convinced that it is seriously problematic. I’ll abandoned this until getting further information.

Thank you again.

5

I found a solution. This is nothing new. Here it is: http://www.kahunaburger.com/2008/10/13/selecting-random-weighted-records-from-mysql/