Why does this SQL query not work? - php

Question

I have been bugging by head over this, but couldn't get this to work. What's wrong with this?
$query="Select studentid,firstname,lastname,pts from students where collegeid=4";
$result=mysql_query($query);
$row=mysql_fetch_array($result);
$pts=$row['pts'];
$name=$row['firstname']." ".$row['lastname'];
$rank= mysql_num_rows(queryMysql("Select distinct pts from students where pts>=$pts"));
echo<<<_END
<a href="student_profile.php?studentid=$row[studentid]" style="text-decoration: none;">
<div class="apps_each your_rank">
<span style="margin-right:5px;">$rank</span>
<div class="dp_small_c"><img class="dp_small" src="upload/$row[studentid].jpg"/></div>
<span class="apps_names">$name</span>
<div style="float:right">
<img src='pts.png' /><span>$row[pts]</span>
<img src='level.png' /><span>Level 1</span>
</div>
</div>
</a>
_END;
The error:
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1.
Surprisingly, below one(removing the WHERE clause) works. Why?
$row=mysql_fetch_array(mysql_query("Select studentid,pts,firstname,lastname from students"));
Table structure:
Everything's fine with table and its columns, because this query works everywhere else, only not here!

Answer 1

You mentionned in the comments that you wanted to use PDO. Here's what you can try:
$username = "enterUsername";
$password = "enterPass";
$conn = new PDO('mysql:host=localhost;dbname=myDatabase', $username, $password);
$query = $conn->prepare("Select studentid,pts,firstname,lastname from students where collegeid=:id");
$query->execute(array(
':id' => 4
));
// get errors if there are
$errors = $query->errorInfo();
echo "<pre>";
print_r($errors);
echo "</pre>";
$results = $query->fetch(PDO::FETCH_ASSOC); // can also be fetchAll if you have more than 1 row.
// to test and check results
echo "<pre>";
print_r($results);
echo "</pre>";

Answer 2

if $query in the question returns an empty row, then the variable beneath it remained unassigned - i.e., $pts and $name have no entities.
However, the query below them uses the variable $pts, which presumably has to store some value - which, when not, throws the above posted MYSQL error. The use of function queryMysql() for this query further clears the issue, as it was defined as below:
function queryMysql($query)
{
$result=mysql_query($query) or die(mysql_error());
return $result;
}
Hence, the MySql error.

Answer 3

I would use this library for all MySQL querying - http://www.meekro.com.
Your select query becomes like this:
// Load Library
require 'meekrodb.2.2.class.php';
// Setup DB Connection
DB::$user = 'my_database_user';
DB::$password = 'my_database_password';
DB::$dbName = 'my_database_name';
DB::$host = '123.111.10.23';
// Where clause
$collegeid = 4;
// Exec Query
$row = DB::queryFirstRow("Select studentid,pts,firstname,lastname from students where collegeid = %d", $collegeid);
src: http://www.meekro.com/docs.php#anchor_queryfirstrow