while循环内未执行更新语句

请帮我一下。

我有一个php代码，首先搜索将需要插入到另一个表的记录

//search for split values (capacitors)
$capacitance =mysql_query("SELECT itemno, wwpn,  SUBSTR(val, 1, LENGTH(val) / 2) as capacitor,
                           SUBSTR(val, LENGTH(val) / 2+1) as capasitance
                           FROM   bom_csv WHERE boardnumber ='$board' and bom_csv.qty<>'' and bom_csv.qty !='qty';");
while($row =mysql_fetch_array($capacitance))
 {
    echo "<pre>";
    echo $row['itemno'];
    echo $row['capacitor'];
    echo $row['capasitance'];
    echo $row['wwpn'];
    echo "</pre>";
    $capacitor = $row['capacitor'];
    $capacity =$row['capasitance'];
    $adi_pn=$row['adi_pn'];
    $itemno=$row['itemno'];
    //insert into via update
    $update =@mysql_query ("UPDATE bom_crunching SET capacitor ='$capacitor', capacitance ='$capacity' WHERE boardmodel ='$board' and adi_pn ='$adi_pn'");
    if ($update)
    {
        echo "OKAY!";
    }
    else
    {
        echo "NOT OKAY!";
    }
 }

在执行它时，我没有得到任何错误。但是，当我查看我的查询浏览器时，它没有插入任何数据。我想要的结果是通过update语句插入表中的所有记录，因为它的默认值为null。

提前感谢!