Question

我想使用下拉列表来排序查询结果。无论在下拉列表中选择何种选项，查询都将按所选选项的升序排序。我的查询工作正常，我只需要包含ORDER BY子句。请仔细查看表格，请帮我解决这个问题。

以下是代码：

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>

<title>Exam Interface</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body>

<form action="exam_interface.php" method="post" name="sessionform">        <!-- This will post the form to its own page"-->
<p>Session ID: <input type="text" name="sessionid" /></p>      <!-- Enter Session Id here-->
<p>Module Number: <input type="text" name="moduleid" /></p>      <!-- Enter Module Id here-->
<p>Teacher Username: <input type="text" name="teacherid" /></p>      <!-- Enter Teacher here-->
<p>Student Username: <input type="text" name="studentid" /></p>      <!-- Enter User Id here-->
<p>Grade: <input type="text" name="grade" /></p>      <!-- Enter Grade here-->
<p>Order Results By: <select name="order">
<option name="noorder">Don't Order Results</option>
<option name="ordersessionid">Session ID</option>
<option name="ordermoduleid">Module Number</option>
<option name="orderteacherid">Teacher Username</option>
<option name="orderstudentid">Student Username</option>
<option name="ordergrade">Grade</option>
</select>
<p><input type="submit" value="Submit" /></p>
</form>

<?php

$username="xxx";
$password="xxx";
$database="mobile_app";

mysql_connect('localhost',$username,$password);

@mysql_select_db($database) or die("Unable to select database");

$sessionid = $_POST['sessionid'];
$moduleid = $_POST['moduleid'];
$teacherid = $_POST['teacherid'];
$studentid = $_POST['studentid'];
$grade = $_POST['grade'];

$result = mysql_query("SELECT * FROM Module m INNER JOIN Session s ON m.ModuleId = s.ModuleId JOIN Grade_Report gr ON s.SessionId = gr.SessionId JOIN Student st ON gr.StudentId = st.StudentId WHERE ('$sessionid' = '' OR gr.SessionId = '$sessionid') AND ('$moduleid' = '' OR m.ModuleId = '$moduleid') AND ('$teacherid' = '' OR s.TeacherId = '$teacherid') AND ('$studentid' = '' OR gr.StudentId = '$studentid') AND ('$grade' = '' OR gr.Grade = '$grade')");

$num=mysql_numrows($result);    

echo "<table border='1'>
<tr>
<th>Student Id</th>
<th>Forename</th>
<th>Session Id</th>
<th>Grade</th>
<th>Mark</th>
<th>Module</th>
<th>Teacher</th>
</tr>";

while ($row = mysql_fetch_array($result)){

 echo "<tr>";
  echo "<td>" . $row['StudentId'] . "</td>";
  echo "<td>" . $row['Forename'] . "</td>";
  echo "<td>" . $row['SessionId'] . "</td>";
  echo "<td>" . $row['Grade'] . "</td>";
  echo "<td>" . $row['Mark'] . "</td>";
  echo "<td>" . $row['ModuleName'] . "</td>";
  echo "<td>" . $row['TeacherId'] . "</td>";
  echo "</tr>";
}

echo "</table>";

mysql_close();


 ?>

</body>
</html>

Answer 1

嗯，ORDER BY子句在WHERE子句之后，所以你只需要在那里添加它，对吧？我建议在给出当前代码的情况下，最简单的方法是使用switch来设置变量的值$orderbyclause，然后将该变量附加到查询的末尾。（default的{{1}}案例应将switch设置为空字符串。）

另外，请阅读有关SQL注入的信息并了解如何防范它。您发布的代码存在很大的安全漏洞。

Answer 2

switch ($_POST['order') {
    case 'ordersessionid': $order_field = 'gr.SessionID'; break;
    case 'ordermoduleid': $order_field = 'whatever'; break;
    ...
    default: $order_field = 'default_field'; break;
}

$sql = "SELECT .... ORDER BY {$order_field} ASC";

您可能想尝试直接将$_POST['order']插入到查询中，表单中包含适当的name=""值，但是......请勿。 Little Bobby Tables将停止访问并永不离开。

如何使用下拉列表排序查询结果

2 个答案: