Question

I have a piece of PHP code that is generating over 6000 queries to mySQL and I have the feeling this could be done a lot better…

$q0 = "SELECT id_productFROM products";     
$e0 = mysql_query($q0) or die("Select failed: " . mysql_error());

while($r0 = mysql_fetch_array($e0)){    

    $id_product = $r0['id_product'];

    $q1 = "SELECT * FROM productspeople WHERE id_product = $id_product ";       
    $e1 = mysql_query($q1) or die("Select failed: " . mysql_error());

    if(mysql_num_rows($e1) == 0){ $count++; }else{ }

}

echo $count. "<br />";

My question is … Is there a better way of counting “non occurences” of a certaing id field of a table in another table? If so .. how?

Thanks in advance and thanks for understanding this (most probably) noobness of mine.

Answer 1

One query.

SELECT COUNT(*) AS count 
  FROM products
 WHERE NOT EXISTS (
         SELECT 1 FROM productspeople WHERE id_product = products.id_product
       )

Oh, and it will help tremendously if there is an index on productspeople.id_product.

As a general tip, try to do as much work as possible on the database. In comparison it is ridiculously inefficient to send queries back and forth between PHP and the DB.