How do I stop duplicate rows on table join in SQL? - php

Question

Trying to join this table, so that i can change the code if the tutor ID matches the session tutor ID. But it shows multiple results in the calendar that its generating.
Below is the current PHP code, although the entries are being duplicated due to having multiple tutor ID's within the table. i'm not sure how to change this.
<?php
$sqlAssignments = "SELECT * FROM tbl_assignments LEFT JOIN tbl_tutorModules ON tbl_assignments.module_code = tbl_tutorModules.module_code"; //
$qryAssignments = mysqli_query($con, $sqlAssignments); // running the query
while($rowAssignment = mysqli_fetch_assoc($qryAssignments)){
if ($_SESSION["ID"] == $rowAssignment['tutor_id']) {
echo "{ title: '" . $rowAssignment['assignment_name'] . "', start: '" . $rowAssignment['hand_in_date'] . "', end: '" . $rowAssignment['hand_in_date'] . "', url: 'view/assignments.php?id=" . $rowAssignment['assignment_id'] . "', color: '#f1f1f1'},";
} else {
echo "{ title: '" . $rowAssignment['assignment_name'] . "', start: '" . $rowAssignment['hand_in_date'] . "', end: '" . $rowAssignment['hand_in_date'] . "', url: 'view/assignments.php?id=" . $rowAssignment['assignment_id'] . "'},";
}
}
?>
The actual results at the moment is that when the tutorModules has multiple tutors, the output duplicates calendar results.
Thanks
Edit: Tables look like this with some example data
tbl_tutorModules
con_id module_code tutor_id
2 ISYS30025 1
3 ISYS30025 2
tbl_assignments
assignment_id
module_code
assignment_name
assignment_weight
set_date
hand_in_date
hand_in_method
assignment_type
This is the current output
The expected output is for these not to be duplicated.

Answer 1

You want to know whether a certain tutor is involved in an assignment. So pass the tutor ID to the DBMS in order to let it find out in a query.
SELECT
assignment_id, assignment_name, hand_in_date,
case when module_code in (SELECT module_code FROM tbl_tutorModules WHERE tutor_id = ?)
then 'yes' else 'no'
end as tutor_involved
FROM tbl_assignments
ORDER BY assignment_id;
As you can see, I don't join the tables, because I'm not interested in the joined result. I merely want to look up a record in tbl_tutorModules. We use IN or EXISTS in SQL to look up records in another table.
See here how to pass parameters to the DBMS in mysqli: http://php.net/manual/en/mysqli.prepare.php