CODEWITHSUNDEEP
phpmysqlsql-order-byswitch-statement
BruceyBandit
BruceyBandit

Reputation: 4334

Using ORDER BY clause to order a query by using values selected from a drop down menu

I want to use a dropdown list to order the query result. Whatever option is chosen in the dropdown list, the query will be ordered in ascending order by the option selected. My query works fine, I just need to include the ORDER BY clause which I know comes after the WHERE clause. Please look at the form carefully and please help me on this problem.

Below is the code:

    <!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>

I have tried using a switch statement which was kindly posted to me but I couldn't get it to work. This is what I tried to do below:

$orderfield = isset ($_POST['order']);
switch ($orderfield) {
    case 'ordersessionid': $orderfield = 'gr.SessionId';
    break;
    case 'ordermoduleid': $orderfield = 'm.ModuleId'; 
    break;
    case 'orderteacherid': $orderfield = 's.TeacherId';
    break;
    case 'orderstudentid': $orderfield = 'gr.StudentId'; 
    break;
    case 'ordergrade': $orderfield = 'gr.Grade';
    break;
}

$result = mysql_query("SELECT * FROM Module m INNER JOIN Session s ON m.ModuleId = s.ModuleId JOIN Grade_Report gr ON s.SessionId = gr.SessionId JOIN Student st ON gr.StudentId = st.StudentId WHERE ('$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 = '$grade') ORDER BY '$orderfield' ASC");

Any help will be much appriciated. Thank You

Upvotes: 1

Views: 227

Answers (2)

Phil
Phil

Reputation: 164894

Try

$orderfield = isset ($_POST['order']) ? $_POST['order'] : 'default order field';

See http://php.net/manual/en/function.isset.php

Update

Just noticed... arguments to the ORDER BY statements aren't parameters but expressions. In other words, lose the single-quotes around $orderfield in your query, ie

... ORDER BY $orderfield ASC");

Upvotes: 2

Mike B
Mike B

Reputation: 32155

Looks like you might have put the wrong attribute on those options. You want value, not name:

<option value="noorder">Don't Order Results</option>

Or... Debug

Find out why it's not working:

$orderfield = isset ($_POST['order']);
switch ($orderfield) {
    case 'ordersessionid': $orderfield = 'gr.SessionId';
    break;
    case 'ordermoduleid': $orderfield = 'm.ModuleId'; 
    break;
    case 'orderteacherid': $orderfield = 's.TeacherId';
    break;
    case 'orderstudentid': $orderfield = 'gr.StudentId'; 
    break;
    case 'ordergrade': $orderfield = 'gr.Grade';
    break;
}

// Debug here by checking the value of $orderfield
// This will tell us if the switch statement did its job
var_dump($orderfield);

// Alternatively, you could set a default case and catch it there

You can also inspect the $_POST array before all this happens. Give this a look and see if all your form values are there:

var_dump($_POST);
die();

Upvotes: 2

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