help with a query - php

Question

i have a function where i get the ratings of the selected user by id,
it gets the ratings from one type of things, the ratings of a diff type of things and then does a+b
i know it's not very optimized but i'm focus on making all work...
this i do it like this
function votos_usuario($id){
$previa = "SELECT id FROM preguntas WHERE id_usuario = '$id'";
$r_previo = mysql_query($previa);
$ids_p = '0, ';
while($items_previos = mysql_fetch_array($r_previo)){
$ids_p .= $items_previos['id'].", ";
//echo "ids pregunta usuario: ".$items_previos['id']."<br>";
}
$ids = substr($ids_p,0,-2);
//echo $ids;
$consulta = "SELECT valor FROM votos_pregunta WHERE id_pregunta IN ( $ids )";
//echo $consulta;
$resultado = mysql_query($consulta);
$votos_preguntas = 0;
while($voto = mysql_fetch_array($resultado)){
$votos_preguntas = $votos_preguntas + $voto['valor'];
}
//$votos_preguntas= 0;
//$votos_preguntas = mysql_query("SELECT SUM(valor) FROM votos_pregunta WHERE id_pregunta IN (SELECT id FROM preguntas WHERE id_usuario = '$id')");
$previa_r = "SELECT id FROM recetas WHERE id_usuario = '$id'";
$r_previo_r = mysql_query($previa_r);
$ids_r = '0, ';
while($items_previos_r = mysql_fetch_array($r_previo_r)){
$ids_r .= $items_previos_r['id'].", ";
//echo "ids pregunta usuario: ".$items_previos['id']."<br>";
}
$ids = substr($ids_r,0,-2);
$consulta_b = "SELECT valor FROM votos_receta WHERE id_receta IN ( $ids )";
//echo $consulta;
$resultado_b = mysql_query($consulta_b);
$votos_recetas = 0;
while($voto_r = mysql_fetch_array($resultado_b)){
$votos_recetas = $votos_recetas + $voto_r['valor'];
}
$total = $votos_preguntas + $votos_recetas;
return $total;
}
Now the Question,
how can i do it to get all users ordered by rating desc ???? i just can't see it :S

Answer 1

SELECT uid, SUM(Votes)
FROM (
SELECT p.id_usuario uid, SUM(vp.valor) votes
FROM preguntas p JOIN votos_pregunta vp ON p.id = vp.id_pregunta
GROUP BY p.id_usuario
UNION ALL
SELECT r.id_usuario uid, SUM(vr.valor) votes
FROM recetas r JOIN votos_receta vr ON r.id = vr.id_receta
GROUP BY r.id_usuario
) rs
GROUP BY uid
ORDER BY SUM(Votes) DESC
instead of your php loop and all the sub queries, you can use this single query to get what you want:
SELECT (
SELECT SUM(vp.valor)
FROM preguntas p JOIN votos_pregunta vp ON p.id = vp.id_pregunta
WHERE p.id_usuario = '$id')
+ (
SELECT SUM(vr.valor)
FROM recetas r JOIN votos_receta vr ON r.id = vr.id_receta
WHERE r.id_usuario = '$id'
)

Answer 2

Also, when you're only using the associative keys in the result array, using mysql_fetch_assoc() is much, much faster than mysql_fetch_array().
Same applies to using mysql_fetch_row() instead when you're just using the numerical keys.