Question

On my site I experience a rather high server load time and I am thinking of ways to optimize some of my mysql queries.

What I do now:

1. First I count all the cars in the table having certain criteria;

2. If the number of cars is greater then 20, I do that query with those criteria;

3. If the number is smaller, I do a more general search just to give some results on the page.

Is there a faster way to do this?

It seems I am loosing performance counting the rows with certain criteria** and querying them once again just to get the data.

$car_sql = mysql_query("SELECT COUNT(*) FROM ".$table." WHERE carid IS NOT NULL $criteria1 $criteria2 $criteria3"); 

$car_nr = mysql_result($car_sql, "0"); 

if($car_nr > 20){ 
    $result = mysql_query("SELECT carid,pic0 FROM ".$table." WHERE carid IS NOT NULL $criteria1 $criteria2 $criteria3");
} else { 
    $result = mysql_query("SELECT carid FROM ".$table." LIMIT 20"); 
}

Any ideas?

Answer 1

You can combine your first and your second query as they are the basically the same:

$car_sql = mysql_query("SELECT SQL_CALC_FOUND_ROWS carid,pic0 FROM ".$table." WHERE carid IS NOT NULL $criteria1 $criteria2 $criteria3");

But you would have to test if that is a lot slower than the first separate query.

It would be faster if the number of results normally is bigger than 20.