Question

I have 3 MySQL tables:

shelf
---------------
id
project_id
label


books
---------------
id
project_id
label


booksOnShelves
---------------
id
shelf_id
book_id
project_id
user_id

I need to display what books are on what shelf in a table format, something like:

History     Fiction
-------     --------
book 1      book 4
book 2      book 5 
book 3

So far I’ve got only this:

  SELECT 
        shelf.label,
        books.label
    FROM booksOnShelves
    LEFT JOIN shelf ON (shelf.id = booksOnShelves.shelf_id)
    LEFT JOIN books ON (books.id = booksOnShelves.book_id) 
    WHERE booksOnShelves.project_id = ".$_POST['pid']."
    AND booksOnShelves.user_id = ".$_POST['uid']."

Couple things… For some odd reason shelf label is not showing up, but if I remove all other parts in the query, like book labels, it works. Also, I can only display in one long column (via loop). How would I break it into separate coulmns, or if in one column, how do I show shelf label only once per group of books?

Answer 1

1st: escaping the input vars

2nd: remove LEFT in join, if you start from cross table leftjoin is nonsense (IMHO)

3rd: use GROUP_CONCAT to return a string of set of titles, comma separated, 1 row per shelf

$pid = mysql_real_escape_string( $_POST['pid'] );
$uid = mysql_real_escape_string( $_POST['uid'] );

$sql = "SELECT 
        shelf.label,
        GROUP_CONCAT( books.label separator ',') as titlelist
    FROM booksOnShelves
    JOIN shelf ON (shelf.id = booksOnShelves.shelf_id)
    JOIN books ON (books.id = booksOnShelves.book_id) 
    WHERE booksOnShelves.project_id = ".$pid."
    AND booksOnShelves.user_id = ".$uid."
group by booksOnShelves.shelf_id";

Of course your PHP has to parse/manage titlelist to fill the page

ADD

You can change the separator as your needs (eg: |) then

foreach($results as $row){

echo "<div class='float_left'><p class='bold'>".$row['label']."</p>\n";
// using '|' as separator less common then ',' in the titles
$array_of_titles = explode('|',$row['titlelist']);
foreach($array_of_titles as $title){
echo "<p>".$title."</p>\n";

}
echo "</div>\n";
}

I hypothesized $results is an associative array with all rows of your query.