performance vraag(1 query vaak uitvoeren, of 1 zware query?)

Ik vroeg mij af of er verschil in snelheid zat, en zoja, hoeveel tussen de volgende 2 constructies.

$result = mysql_query("SELECT `id` FROM `tabel1` WHERE `parent`=" . addslashes($_GET['cat']));
while($row = mysql_fetch_assoc($result)){

$result2 = mysql_query("SELECT `id` FROM `tabel1` WHERE `parent`=" . $row['id']);
while($row2 = mysql_fetch_assoc($result2)){

#doe iets

}

}

of

$array = array();
$result = mysql_query("SELECT `id` FROM `tabel1` WHERE `parent`=" . addslashes($_GET['cat']));
while($row[] = mysql_fetch_assoc($result)){

$array[] = $row[count($row) - 1]['id']

}
$result2 = mysql_query("SELECT `id` FROM `tabel1` WHERE `parent` IN(" . implode(', ', $array[]) . ")");
while($row2 = mysql_fetch_assoc($result2)){

#doe iets

}