Get data from a join table - php

Question

I am trying to pull data from my database which ahs the following:
x3 tables:
docs
doc_id - index
cat
cat_id - index
doc_cat_join
doc_id - foreign key to docs/doc_id
cat_id - foreign key to cats/cat_id
I have inserted some data so that I have a row in cats and a rows in docs and in the join table bound a cat_id with a doc_id which all works fine. I am tying to pull that from the tables and show it, here is my approach so far but not getting anything out and am wondering where my failings are as I am getting no errors?
when I visit the cateroy page in my scripts I GET the id from the url:
$id = $_GET['cat_id'];
$q = sprintf("
SELECT
docs.doc_id,doc_name
FROM docs
INNER JOIN doc_cat_join
ON cats.cat_id = doc_cat_join.cat_id
WHERE doc_cat_join.doc_id = '%s'
",
mysqli_real_escape_string($dbc, $id) );
$r = mysqli_query($dbc,$q)
or die ("Couldn't execute query: ".mysqli_error($dbc));
// FETCH AND PRINT ALL THE RECORDS
echo '<div class="view_body">';
while ($row = mysqli_fetch_array($r)) {
echo ' '.$row["doc_name"]. '<br>';
}
echo '</div>';
}
for some bizarre reason I get nothing, if I do a var_dump on $r I get the following:
string(168) " SELECT docs.doc_id,doc_name FROM docs INNER JOIN doc_cat_join ON cats.cat_id = doc_cat_join.cat_id WHERE doc_cat_join.doc_id = '24' "
So it gets the correct category ID I am in.
I am now getting th following output:
Couldn't execute query: Unknown column 'cats.cat_id' in 'on clause'

Answer 1

as per your input and query design, your query should be as per below-
SELECT d.doc_id, d.doc_name
FROM docs AS d
INNER JOIN doc_cat_join AS dc ON dc.doc_id = d.doc_id WHERE dc.cat_id = '24';
Note: If it is not then show what output you require.

Answer 2

$id = $_GET['cat_id'];
$q = sprintf("
SELECT
*
FROM docs
INNER JOIN doc_cat_join
ON docs.doc_id = doc_cat_join.doc_id
INNER JOIN cat
ON doc_cat_join.cat_id = cat.cat_id
WHERE doc_cat_join.cat_id = '$id'
",
mysqli_real_escape_string($dbc, $id) );
print_r ($q);
// FETCH AND PRINT ALL THE RECORDS
echo '<div class="view_body">';
while ($row = mysqli_fetch_array($r)) {
echo ' '.$row["doc_name"]. '<br>';
}
echo '</div>';
}
your query is wrong I think.