Sorted output of a joined MySQL result in PHP - php

Question

Doing an allnighter on a project and my mind is blank atm... Simple question really:
I have two MySQL tables, product and category. Each product belongs to exactly one category. Every category has several products.
SELECT
p.uid as product_uid, p.name_NL as product_name, p.price as product_price,
c.uid as category_uid, c.name_NL as category_name
FROM
product p, category c
WHERE
p.category_uid = c.uid
This gives me a nice overview of all products in their respective category. My question is about outputting this data on the page. I'm aiming for this:
<h1>Category name</h1>
<p>Product in this category</p>
<p>Other product in this category</p>
<h1>Next category</h1>
<p>Product in next category</p>
My mind is completely blank right now. How would one go about doing this?
I would like to avoid doing subqueries (if possible).
Kind regards,
M

Answer 1

What about adding ORDER BY category_uid so that the products are ordered by category in your SQL query. Then using PHP, loop through each product (row) and when you encounter a new category, add a new header.
Example:
<?php
// ...
$previous_category_uid = null;
// Loop through each row.
while ( $row = $result->fetch_assoc() )
{
// If the category UID is not the same as the one from the previous row, add a header.
if ( $previous_category_uid != $row['category_uid'] )
{
echo '<h1>' . $row['category_name'] . '</h1>';
$previous_category_uid = $row['category_uid'];
}
}
The benefit of this method is that you don't have to nest queries. A single query will suffice.

Answer 2

Don't you just need to use a GROUP BY category_uid ?

Answer 3

Generally speaking you have two options:
Get all the data at once (like you are doing currently) then use PHP to either pre-sort the data by category. Then do your output looping over this array. So 1 query, 2 + n loops (where n is the number of categories).
Get all your categories and then loop over those for output. In each iteration you will need to query all products for that loop. So 1 + n queries, 1 + n loops (where, again, n is the number of categories).
Option 2 might be more straightforward, but clearly there are more queries. In the end, it's your call.

Answer 4

Assuming you're looking for alphabetical ordering for category names and products within each category:
SELECT
p.uid as product_uid, p.name_NL as product_name, p.price as product_price,
c.uid as category_uid, c.name_NL as category_name
FROM product p INNER JOIN category c ON p.category_uid = c.uid
ORDER BY category_name, product_name
This also converts your query's Cartesian product and WHERE to an inner join.
To output with the headers you want, just loop over the returned rows, and keep track of the category you're in. Whenever the category of the current row is different from the previous one, you print a new h1 for the new category and update the stored "current" category.