PHP MySQL get data from 2 tables - php

Question

I am trying to combine 2 tables from my database:
files table:
id
file_name
file_description
file_url
access_files table:
id
student_id
file_id
Here is my sql code, currently getting all files from the files table, it doesn`t show the selected files for the user.
<?php
$SQL = "SELECT * FROM files, access_files WHERE student_id ='$studentid'";
$result = mysql_query($SQL);
while ($db_field = mysql_fetch_assoc($result)) {
?>
<div class="accordion-group">
<div class="accordion-heading">
<a href="#<?php print $db_field['file_id']; ?>" data-parent="#accordion" data-toggle="collapse" class="accordion-toggle collapsed">
<?php print $db_field['file_name']; ?>
</a>
</div>
<div class="accordion-body collapse in" id="<?php print $db_field['file_id']; ?>">
<div class="accordion-inner">
<?php print $db_field['file_description']; ?><br/><br/>
Download File Now!
<br/><br/>
</div>
</div>
</div>
<?php } ?>
The code is suppose to show only the files associated to the user.

Answer 1

What you need to do is JOIN the tables.
Most common types of JOINs:
INNER JOIN - Used to match data where it can match the ON () statement. If the ON() doesn't match, the result will be excluded.
LEFT JOIN - Used if the data you match in the ON() doesn't have to be there. It just appends the data to the original FROM, and fills columns with NULL if no data is matched.
Example
SELECT
ft.id,
ft.file_name,
ft.file_description,
ft.file_url,
af.id as access_id,
af.student_id,
af.file_id
FROM
files ft
INNER JOIN access_files af ON ( ft.id = af.file_id )
WHERE
fa.student_id = '$studentid'

Answer 2

You are making a classic cartesian join with your query:
SELECT * FROM files, access_files WHERE student_id ='$studentid'
You need to specify how the two tables are connected:
SELECT * FROM files a, access_files b WHERE a.student_id ='$studentid' and b.studentID=a.student_id
If you don't specify the link - or don't have one, the database will try to link every single row in the first table with every single row in the second.

Answer 3

Join your tables.
SELECT table1.*, table2.*
FROM table1
LEFT JOIN table1.pk = table2.fk
WHERE table1.pk = 1;