Merge result after query with JOIN clause in Mysql - php

Question

I have two table like this:
Product
id | title
-------------------------------
1 | Skirt
2 | Pants
Product_thumbnail
id | product_id | image
-------------------------------
1 | 1 | pant.jpg
2 | 1 | shoes.png
When I want to get product with the thumbnail, I query like this:
SELECT p.*, pt.image FROM product p
LEFT JOIN product_thumbnail pt ON pt.product_id = p.id;
The output I expected
[0]=> [
[id] => 1
[image] =>
[
[0] => pant.jpg
[1] => shoes.jpg
]
]
[1]=> [
[id] => 2
[image] => null
]
But the real output
[0]=> [
id => 1
image => pant.jpg
]
[1]=> [
id => 1
image => shoes.jpg
]
[2]=> [
id => 2
image => shoes.jpg
]
As you see, there is 2 element duplicate, so I need to merge it by hand, is there any way to achieve this more easy? Because my table have many tables relate together more than this, I'm using PHP, I use array_merge_recursive() to merge them but if do like that I get duplicate value in each field, like this:
[0]=> [
[id] =>
[
[0] => 1
[1] => 1
]
[image] =>
[
[0] => pant.jpg
[1] => shoes.jpg
]
]
It's not what I want, can anyone give me an idea?

Answer 1

Consider the following. The code could I'm sure be written more economically, but hopefully you get the idea...
<?php
/*
DROP TABLE IF EXISTS product;
CREATE TABLE product
(id SERIAL PRIMARY KEY
,title VARCHAR(12) NOT NULL UNIQUE
);
INSERT INTO product VALUES
(1,'Hat'),
(2,'Shoe');
DROP TABLE IF EXISTS product_thumbnail;
CREATE TABLE product_thumbnail
(id SERIAL PRIMARY KEY
,product_id INT NOT NULL
,image VARCHAR(12) NOT NULL UNIQUE
);
INSERT INTO product_thumbnail VALUES
(1,1,'sombrero.jpg'),
(2,1,'stetson.png');
SELECT p.id
, p.title
, t.image
FROM product p
LEFT
JOIN product_thumbnail t
ON t.product_id = p.id;
+----+-------+--------------+
| id | title | image |
+----+-------+--------------+
| 1 | Hat | sombrero.jpg |
| 1 | Hat | stetson.png |
| 2 | Shoe | NULL |
+----+-------+--------------+
*/
require('path/to/connection/stateme.nts');
$query = "
SELECT p.id
, p.title
, t.image
FROM product p
LEFT
JOIN product_thumbnail t
ON t.product_id = p.id;
";
$result = mysqli_query($db,$query);
$old_array = array();
while($row = mysqli_fetch_assoc($result)){
$old_array[] = $row;
}
$new_array = array();
foreach ($old_array as $row) {
$new_array[$row['id']]['title'] = $row['title'];
$new_array[$row['id']]['image'][] = $row['image'];
}
$new_array = array_values($new_array); // reindex
print_r($new_array);
?>
Outputs
Array
(
[0] => Array
(
[title] => Hat
[image] => Array
(
[0] => sombrero.jpg
[1] => stetson.png
)
)
[1] => Array
(
[title] => Shoe
[image] => Array
(
[0] =>
)
)
)

Answer 2

MySQL doesn't support arrays, but you can aggregate the data into a string:
SELECT p.*, GROUP_CONCAT(pt.image) as images
FROM product p LEFT JOIN
product_thumbnail pt
ON pt.product_id = p.id
GROUP BY p.id;
Note that aggregating only by the id and selecting p.* is allowed and even standard SQL -- assuming that id is a primary key or declared to be unique. This is the one situation when this syntax is permitted.