Varbūt šāds pieprasījums būtu optimālāks.
for($i=1; $i<=12; $i++){
$month = mktime(0,0,0, $i, 1, 2008);
$month2 = mktime(0,0,0, $i, date('t', $month), 2008);
$query = 'SELECT COUNT(*), SUM(apmekletaji), SUM(pirkumi) FROM `tabula` WHERE `datums`>='.$month.' AND `datums`<='.$month2;
$results = mysql_query($query);
$row = mysql_fetch_row($results);
echo date('m', $month).' '.$row[0];
}