Sæt flere tables sammen og sorter dem

Kode 

$show=10;
$historier_res = mysql_query("SELECT * FROM historier ORDER BY timestamp DESC LIMIT ".$show);
$artikler_res =  mysql_query("SELECT * FROM artikler ORDER BY timestamp DESC LIMIT ".".$show);
$shout_res = mysql_query("SELECT * FROM shout ORDER BY timestamp DESC LIMIT ".$show);


$mix=array(
 array('hist',mysql_fetch_row($historier_res),$historier_res),
array('arti',mysql_fetch_row($artikler_res),$artikler_res),
array('shou',mysql_fetch_row($shout_res),$shout_res)
);
$result=array();
for($i=0;$i<$show;$i++){  
  $temp=null;
  for($p=0;$p<count($mix);$p++){
    if($temp==null){
      if($mix[$p][1]){
        $temp=$p;
      }
    }else{
      if(!$mix[$p][1]){
        continue;
      }
      if{$mix[$p][1]['timestamp']>$mix[$temp][1]['timestamp']){
        temp=$p;
       }
    }
  }
  if($temp==null){
    break;
  }
  $r=$mix[$temp][1];
  $r['type']=$mix[$temp][0];
  $mix[$temp][1]=mysql_fetch_row($mix[$temp][2]);
  $mix[$temp][1]['timestamp']=(int)$mix[$temp][1]['timestamp'];
  $result[]=$r;

}

SQL kode 

 SELECT *.....
 UNION
 SELECT *.....
 UNION
 SELECT *.....