Question

I have been reading about speed issues in relation to getting a random row via MYSQL and PHP, and wondered how my code might be improved for speed.

I have banner information in my database in a table called “banners” and i want to display a random banner in relation to the position on the page, and add +1 to the view_count for that banner. My method works, but for a busy site where this happens on each page load, can this be improved for speed? Thanks

/* Get banners for position 1 then choose a random one to display  */
$banners = mysql_query("SELECT id,title,banner_url,destination FROM ".TBL_BANNERS." WHERE position = '1' AND status = '1'");
$banner_count = mysql_num_rows($banners) - 1;
$rand_offset = mt_rand(0,$banner_count);
$result = mysql_query("SELECT id,title,banner_url,destination FROM ".TBL_BANNERS." LIMIT $rand_offset, 1 "); 

$banner_id = mysql_result($result,0,"id");
$banner_title = mysql_result($result,0,"title");
$banner_url = mysql_result($result,0,"banner_url");
$banner_dest = mysql_result($result,0,"destination");

/* Add view to this banner */
$database->addViewToBanner($banner_id);

The last function uses the query:

    "UPDATE banners SET view_count = view_count+1 WHERE id = '$banner_id'"

I also need to say, that there probably wont be any more than 100 records in the “banners” table at any one time but there will be holes in the ID. The IDs might go up to say 200 but only half of those will still exist.

Answer 1

Generate a random number in php and drill it that way into the PK

The SQL would be

SELECT id,title,banner_url,destination 
FROM TBL_BANNERS 
WHERE id = $rand_offset

If you miss, run it again. This gives a very efficient seek to one row which will be better than using limit/offset processing