Echo all results from sql join when using group by - php

Question

I have the following query which I run via PHP:
select
{$tableProducts}.*,
{$tableImages}.*
from {$tableProducts}
left join {$tableImages}
on {$tableImages}.product_id = {$tableProducts}.product_id
group by {$tableProducts}.product_id;
Each product (from product table) can have several images (in images table). I loop through the results with a simple while statement:
while($row = $results->fetch_object()) {
echo $row->product_name; // Product table
echo $row->image_src; // Image table
}
Problem: Only the first image of each product is printed, but I want to display all of them. All images are printed if I remove the "order by" part, but then the product_name is printed once for each image (so if one product has three images, the product_name would be printed three times as well).
How do I best solve this?

Answer 1

That's how GROUP BY works.
If you want to get all images for all products, you can solve that (at least) 3 ways:
1: Do not use GROUP BY, handle it in the loop, like:
$last_product = null;
while($row = $results->fetch_object()) {
if ($last_product !== $row->product_id) {
// new product starts here
$last_product = $row->product_id;
echo $row->product_name; // Product table
}
echo $row->image_src; // Image table
}
2: Use GROUP BY & query all images with different statements within the loop.
$products = <query products>;
while($row = $products->fetch_object()) {
echo $row->product_name; // Product table
$images = <query images for product in $row>;
while($row = $images->fetch_object()) {
echo $row->image_src; // Image table
}
}
3: Use aggregate string functions to get all images for a product. This is only works in special cases, f.ex. here, as URL cannot consist new lines, for example.
In MySQL:
select
{$tableProducts}.*,
group_concat({$tableImages}.image_src SEPARATOR '\n') as image_srcs
from {$tableProducts}
left join {$tableImages}
on {$tableImages}.product_id = {$tableProducts}.product_id
group by {$tableProducts}.product_id;
In PostgreSQL:
select
{$tableProducts}.*,
string_agg({$tableImages}.image_src, '\n') as image_srcs
from {$tableProducts}
left join {$tableImages}
on {$tableImages}.product_id = {$tableProducts}.product_id
group by {$tableProducts}.product_id;
In the loop:
while($row = $products->fetch_object()) {
echo $row->product_name; // Product table
foreach (explode("\n", $row->image_srcs) as $image_src) {
echo $image_src; // Image table
}
}