Question

I have two tables in one database. I am querying the first table limit by 10 then loop the results. And inside the while loop, I am doing again another query using a data from the first query as a parameter. Here is an example of the script:

<?php

    $con = mysql_connect(host,username,password);
    mysql_select_db(game_server);

    //My first query
    $q1 = mysql_query('SELECT * FROM game_characters ORDER BY score DESC LIMIT 10');

    while($character = mysql_fetch_object($q1)){
    //My second query
        $q2 = mysql_query('SELECT * FROM game_board WHERE id="'.$character->id.'"');
        $player = mysql_fetch_object($q2);
    }
?>

So if I have a result of 100 rows, then the second query will execute 100 times. And I know it is not good. How can I make it better. Is there a way to do everything in one query? What if there is another query inside the while loop where a data from the second query as a parameter is used?

P.S.: I am doing a rankings system for an online game.

Answer 1

You can do it in one query if you use JOINs.

SELECT * FROM game_board AS b 
    LEFT JOIN game_characters AS c ON b.id = c.id 
ORDER BY c.score DESC 
LIMIT 10

You can also use nested query

SELECT * FROM game_board AS b WHERE 
  id IN (SELECT id FROM game_characters AS c ORDER BY score DESC LIMIT 10)

You can also put all game_character.id into an array, and use

$sql = "SELECT * FROM game_board AS b WHERE b.id IN (" . implode(', ', $game_character_ids) . ")";