Why can I not pull this field? Php / Mysql

Why can't i pull this field pID from the the database?

I have the following php:

<?php
// Get course information cID, prefix, code and dept info : name
$cID = filter_input(INPUT_GET, 'cID', FILTER_SANITIZE_NUMBER_INT);
if(!$cID) {
    echo "No cID specified.";
    exit;
}
require_once('inc/dbc1.php');
$pdo4 = new PDO('my开发者_C百科sql:host=localhost;dbname=###', $username, $password);
$pdo4->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
$sth4 = $pdo4->prepare('
    SELECT fname, lname
    FROM Course Cou, Comment Comm, Professor P
    WHERE Cou.cID = ?
    AND P.pID = Comm.pID
    GROUP BY concat(fname, lname);
    ');
$sth4->execute(array(
    $cID
));
?>

HTML/PHP

<a href='prof.php?pID={$row['pID']}' title='Drexel Professor Comments for {$row['fname']} {$row['lname']}'>

The above is pulling the fname and lname fields, but the first call for pID is not being pulled.

• If I add pID to the select statement, it gives me the ambiguous pID error

  .

Anyone??

You need to add the field to the select statement, otherwise it won't be part of the result set.

If I add pID to the select statement, it gives me the ambiguous pID error

Then make it unambiguous:

 SELECT fname, lname, P.pID

should work.

Add P.pID to your select statement since it is defined in two tables:

select P.pID
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