รบกวนดูให้หน่อยค่ะ โค้ดใช้งานได้ แต่พอช่วง 6แสน มันไม่ขึ้นเลย

if ($price1=='')
$sql="SELECT * FROM car WHERE   price";
else{
	$sql="SELECT * FROM car WHERE price  between '$price1' and '$price2' ";
//$sql="SELECT * FROM car WHERE   'price< $price1' and 'price< $price2' ";
}

echo $sql;

if ($price1=='')
$sql="SELECT * FROM car WHERE   price";
else{
	//$sql="SELECT * FROM car WHERE price  between '$price1' and '$price2' ";
$sql="SELECT * FROM car WHERE   'price > $price1' and 'price < $price2' ";
}

echo $sql;

if ($price1=='')
$sql="SELECT * FROM car WHERE   price";
else{
	$sql="SELECT * FROM car WHERE price  between '$price1' and '$price2' ";
//$sql="SELECT * FROM car WHERE   price > '$price1' and price< '$price2' ";
}

echo $sql;

$price2=$_POST['price1']+199999;

SELECT * FROM car WHERE price  between '600000' and '800000' 

$dbquery = mysql_db_query($db,$sql); 
$num_rows = mysql_num_rows($dbquery);
$i=1;
while ($i<$num_rows){
$result=mysql_fetch_array($dbquery);
$carID=$result["carID"];
$brand=$result["brand"];
$price=$result["price"];
?>
<table width="600" border="0" cellpadding="0" cellspacing="0">
  <tr>
    <td><? echo $i; ?></td>
    <td><? echo $brand;?></td>
    <td><? echo $price;?></td>
  <td><? echo $price1;?></td>
        <td><? echo $price2;?></td>
  </tr>
</table>

$dbquery = mysql_query($sql); 
$num_rows = mysql_num_rows($dbquery);
?>
<table width="600" border="0" cellpadding="0" cellspacing="0">
<?php
$i=1;
while ($result=mysql_fetch_array($dbquery)){
$carID=$result["carID"];
$brand=$result["brand"];
$price=$result["price"];
?>
  <tr>
    <td><? echo ++$i; ?></td>
    <td><? echo $brand;?></td>
    <td><? echo $price;?></td>
    <td><? echo $price1;?></td>
    <td><? echo $price2;?></td>
  </tr>
<?php
}
?>
</table>