php - 期望参数

Question

我的连接查询有问题..我不知道问题出在哪里是我的查询是错误的还是其他什么但是它给出的错误是

Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in     C:\xampp\htdocs\project\teacher\courses-list.php on line 46

这是我的代码，请修改我找不到问题的代码.. :( 类(class)列表.php

<?php
 if ($_SESSION["isteacher"])
{

$con=mysql_connect($dbserver,$dbusername,$dbpassword);
if (!$con)
{
die('Could not connect: ' . mysql_error());

}
mysql_select_db($dbname, $con);
$result = mysql_query("SELECT courses.id AS cid, courses.title, courses.description,    courses.subjects-id, subjects.id AS sid, subjects.subjectname AS sname FROM courses,    subjects WHERE (courses.subjects-id==subjects.id)");
echo "<table border='1'> <br />
<tr>
<th>ID:</th>
<th>Course Name</th>
<th>Description</th>
<th>Subject-ID</th>
<th>EDIT</th>
<th>DELETE</th>
</tr>";

while($row = mysql_fetch_array($result)) // this is the error line
{
echo "<tr>";
echo "<td>" . $row['cid'] . "</td>";
echo "<td>" . $row['title'] . "</td>";
echo "<td>" . $row['description'] . "</td>";
echo "<td>" . $row['sname'] . "</td>";
echo "<td><a href='courses-edit.php?id=" . $row['id']."'>EDIT</a></td>";
echo "<td><a href='courses-delete.php?id=" . $row['id']."'>DELETE</a></td>";
echo "</tr>";
}
echo "</table>";

mysql_close($con);
?>

Answer 1

这里是错误

 $result = mysql_query("SELECT courses.id AS cid, courses.title, courses.description,    courses.subjects-id, subjects.id AS sid, subjects.subjectname AS sname FROM courses,    subjects WHERE (courses.subjects-id==subjects.id)");

应该是

$result = mysql_query("SELECT courses.id AS cid, courses.title, courses.description,    courses.subjects-id, subjects.id AS sid, subjects.subjectname AS sname FROM courses,    subjects WHERE (courses.subjects-id=subjects.id)");

错误部分是

subjects WHERE (courses.subjects-id==subjects.id)");
        here is the error ---------^^--------sould be =

还有please avoid even dont use the mysql_* even the php manual show the message about that use the mysqli or PDO