Can't get my delete statement to work...

MjM8082 · August 16, 2011

I am not seeing what I'm doing wrong. When I click on a check box for the Course class I want to delete.. it just says can't delete. I had this working before, but now its not working.

here is the update_user page with the DELETE statement on it...

<html>
<head>
<title>Update User</title>
</head>
<body>
<form method="post" action="update_user.php">
<?php
$dbc = mysqli_connect('localhost', 'se266_user', 'pwd', 'se266') 
	or die(mysql_error());
//delete users
echo '<b>Delete or Update User</b>.<br />';
if (isset($_POST['remove']))
{          
	foreach($_POST['delete'] as $delete_id)
	{             
		$query = "DELETE FROM users WHERE course_id = $delete_id";             
		mysqli_query($dbc, $query) or die ('can\'t delete user');          
	}        
	echo 'user has been deleted.<br />';   
}
else if (isset($_POST['update']))
{          
	foreach($_POST['update'] as $update_id)
	{             
		$query = "UPDATE FROM users WHERE user_id = $update_id";             
		mysqli_query($dbc, $query) or die ('can\'t update user');          

		$course_id 	= $_POST['course_id'];
		$course_name = $_POST['course_name'];
		$student_id = $_POST['student_id'];

		$sql = "INSERT INTO users (course_id, course_name, student_id) VALUES ('$course_id', '$course_name', '$student_id');"; // added missing single quotes
		$db->exec($sql);

	}				
	echo 'user has been updated.<br />';   
}
//display users info with checkbox to delete  
$query = "SELECT * FROM users";  
$result = mysqli_query($dbc, $query);  
while($row = mysqli_fetch_array($result))
{      
	echo '<input type="checkbox" value="' .$row['course_id'] . '" name="delete[]" />'; 
	echo ' ' .$row['course_name'] .' '. $row['student_id'];
	echo '<br />';  
}
mysqli_close($dbc);

?>	
<input type="submit" name="remove" value="Remove" />
<input type="submit" name="update" value="Update" />
<br>
<br>
<form method="POST" action="update_user2.php">		
<label for="course_id">Course ID:</label> 
<input type="text" id="course_id" name="course_id" /><br />		
<label for="course_name">Course Name:</label>
<input type="text" id="course_name" name="course_name" /><br />

<label for="course_name">Student ID:</label>

<input type="text" id="student_id" name="student_id" /><br />		



</form>
</body>
</html>

And this is the form page if needed...

<?php 
error_reporting(E_ALL); // add maximum error reporting for debugging
?>
<!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">

<!-- the head section -->
<head>
    <title>Lab 3</title>
    
</head>

<!-- the body section -->
<body>
<h1> <i> Add Course </i></h1>
    <?php
	require_once('database.php');
	if (isset($_POST['btn_add']))
	{
                       			
		$course_id 	= $_POST['course_id'];
		$course_name = $_POST['course_name'];
		$student_id = $_POST['student_id'];

		$sql = "INSERT INTO users (course_id, course_name, student_id) VALUES ('$course_id', '$course_name', '$student_id');"; // added missing single quotes
		$db->exec($sql);
	}		
	$query = "SELECT * FROM users";
	$users = $db->query($query);
	// display each of these users
	echo "<ul>";
                
	foreach ($users as $u) 
	{
		$course = $u['course_id'];
		$name  = $u['course_name'];
		$id	   = $u['student_id'];
		echo "<li><a href='update_user2.php?id=$id'>$course $name</a></li>";
	}
	echo "</ul>";

?>
<hr />

<form method="POST" action="lab3.php">		
<label for="course_id">Course ID:</label> 
<input type="text" id="course_id" name="course_id" /><br />		
<label for="course_name">Course Name:</label>
<input type="text" id="course_name" name="course_name" /><br />

<label for="course_name">Student ID:</label>

<input type="text" id="student_id" name="student_id" /><br />		


<input type="submit" value="Add Course" name="btn_add" />			
</form> 
</body>
</html>

PFMaBiSmAd · August 16, 2011

Your die() statement (which is only useful for troubleshooting purposes BTW) needs to tell you why the query failed and what the query is. Try this -

mysqli_query($dbc, $query) or die ("Can't delete user. Query: $query, Error: " . mysqli_error($dbc));

You are actually kind of lucky that it is not deleting anything because the query you are using will delete all the students with a specific course_id (assuming that the course_id column is not an auto-increment id for that table), not just the row with the student_id that you picked.

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Can't get my delete statement to work...

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