ขอสอบถาม เรื่อง การ select เมื่อได้ค่ามาแล้ว จำนำไปเปรียบเทียบ กับ table อื่น ต่อไปครับ

$sql = mysql_db_query($dbname,"SELECT a.pid, a.qty, b.* FROM book a JOIN book2 b ON a.pid=b.pid where a.date = '2010-10-20' GROUP BY a.id ");

$temp_pid = 0;
$bbb = 0;
while($sto = mysql_fetch_array($sql)){
   $aaa = $sto[0];////pid
   if($temp_pid != 0 && $temp_pid != $aaa) {
       echo "$aaa    จำนวน   $bbb <br>";
       $bbb = 0;
       $temp_pid = $aaa;
   }
   $bbb += $sto[1];/// SUM   QTY
}
echo "$aaa    จำนวน   $bbb ";

$sql = mysql_db_query($dbname,"SELECT  book.pid, book.qty, book2.  * FROM book   
JOIN  book2   
ON book.pid=book2.pid 

where book.date =  '2010-10-20'
GROUP BY bale.pid ");

$temp_pid = 0;
$bbb = 0;
while($sto = mysql_fetch_array($sql)){
   $aaa = $sto[0];////pid
   if($temp_pid != 0 && $temp_pid != $aaa) {
      echo "$aaa    จำนวน   $bbb <br>";
       $bbb = 0;
       $temp_pid = $aaa;
   }
   $bbb += $sto[1];/// SUM   QTY
}
echo "$aaa    จำนวน   $bbb ";

$sql = mysql_db_query($dbname,"SELECT  book.pid, book.qty, book2.  * FROM book   
JOIN  book2   
ON book.pid=book2.pid 

where book.date =  '2010-10-20'
GROUP BY book.pid ");

$temp_pid = 0;
$bbb = 0;
while($sto = mysql_fetch_array($sql)){
   $aaa = $sto[0];////pid
   if($temp_pid != 0 && $temp_pid != $aaa) {
      echo "$aaa    จำนวน   $bbb <br>";
       $bbb = 0;
       $temp_pid = $aaa;
   }
   $bbb += $sto[1];/// SUM   QTY
}
echo "$aaa    จำนวน   $bbb ";