mysql_num_rows() 期望参数 1 是资源，布尔值在 C:\wamp\www 中给出 [英] mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\wamp\www

问题描述

代码在几页上运行良好，并显示某种警告，例如mysql_num_rows() 期望参数 1 为资源，布尔值在 C:\wamp\www"中给出...它总是让我感到困惑，因为它正在为某些页面并在某些时候显示了一条警告消息，这让我很沮丧...请帮助...

The code is working fine with few pages and shows some sort warning like "mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\wamp\www"... it always confuses me because it is working for some page and at some point shows a warning message which frustrates me a lot...help please...

<?php 
    $emp_id=$_SESSION['username'];
    $s=mysql_query("select semester from faculty_advisor where emp_id = '$emp_id' ");
    echo $s; //just to check if am getting the correct value
    $subject=mysql_query("select * from subject_list where semester=$s");
    $numrows=mysql_num_rows($subject);
    if($numrows!=0)
    {
        while($row=mysql_fetch_array($numrows))
        {
            ?>
        <td align="center"><?php echo  $row['sid']; ?></td>
        <td align="center"><?php echo  $row['subject_name']; ?></td>
    <td align="center"><?php echo  "<a class='tooltip' href=\"fac_adv_reg_confrm.php?uid=".$row['sid']."\">Edit<span>Edit User Details</span></a>"?></td>  
            <?php
        }
    }
    else
    {
   die('Error: ' . mysql_error());
    }

    ?>

推荐答案

$s=mysql_query("select semester from faculty_advisor where emp_id = 'macs410' ");
echo $s;
$subject=mysql_query("select * from subject_list where semester=$s");

Should be

$s=mysql_query("select semester from faculty_advisor where emp_id = 'macs410' ");
$row = mysql_fetch_assoc($s); 
$subject=mysql_query("select * from subject_list where semester='".$row['semester']."'");

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