Mysql - Add row as column - mysql

Question

I am having a table called listings. A listing can have 2 images, a front and a back-image.
I currently join the tables and get the following output:
**Schema (MySQL v5.7)**
CREATE TABLE `images` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`listings_id` int(11) DEFAULT NULL,
`file_name` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
`properties` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
`created_at` timestamp NULL DEFAULT NULL,
`updated_at` timestamp NULL DEFAULT NULL,
PRIMARY KEY (`id`)
);
CREATE TABLE `listings` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`title` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
`price` double(8,2) NOT NULL,
`created_at` timestamp NULL DEFAULT NULL,
`updated_at` timestamp NULL DEFAULT NULL,
PRIMARY KEY (`id`)
);
INSERT INTO images (id, listings_id, file_name, properties, created_at, updated_at) VALUES(1, 1, 'trv_front.png', '[{"front_back":"front","path":null}]', '2021-10-16 07:08:06', '2021-10-16 07:08:06');
INSERT INTO images (id, listings_id, file_name, properties, created_at, updated_at) VALUES(2, 2, '20211016070806_trv.png', '[{"front_back":"front","path":null}]', '2021-10-16 07:08:06', '2021-10-16 07:08:06');
INSERT INTO images (id, listings_id, file_name, properties, created_at, updated_at) VALUES(3, 1, '2_rv.png', '[{"front_back":"back","path":null}]','2021-10-16 07:08:06', '2021-10-16 07:08:06');
INSERT INTO images (id, listings_id, file_name, properties, created_at, updated_at) VALUES(4, 2, 'backd.png', '[{"front_back":"back","path":null}]','2021-10-16 07:08:06', '2021-10-16 07:08:06');
INSERT INTO listings (id, title, price, created_at, updated_at) VALUES(1, 'test1', 10, '2021-10-16 08:14:08', '2021-10-16 08:14:08');
INSERT INTO listings (id, title, price, created_at, updated_at) VALUES(2, 'test2', 42, '2021-10-16 08:14:08', '2021-10-16 08:14:08');
INSERT INTO listings (id, title, price, created_at, updated_at) VALUES(3, 'test3', 43, '2021-10-16 08:14:08', '2021-10-16 08:14:08');
INSERT INTO listings (id, title, price, created_at, updated_at) VALUES(4, 'test4', 50, '2021-10-16 08:14:08', '2021-10-16 08:14:08');
---
**Query #1**
select l.id, l.title, i.file_name, i.listings_id, i.properties from listings l
left join images i on i.listings_id = l.id order by l.id;
| id | title | file_name | listings_id | properties |
| --- | ----- | ---------------------- | ----------- | ------------------------------------ |
| 1 | test1 | trv_front.png | 1 | [{"front_back":"front","path":null}] |
| 1 | test1 | 2_rv.png | 1 | [{"front_back":"back","path":null}] |
| 2 | test2 | 20211016070806_trv.png | 2 | [{"front_back":"front","path":null}] |
| 2 | test2 | backd.png | 2 | [{"front_back":"back","path":null}] |
| 3 | test3 | | | |
| 4 | test4 | | | |
As you can see in the properties-column there I can see if the image is front or the back side.
However, I would like to get the following structure adding the two columns front_image and back_image:
| id | title | file_name | listings_id | front_image | back_image |
|----|-------|------------------------|-------------|-------------------------|------------|
| 1 | test1 | trv_front.png | 1 | trv_front.png | 2_rv.png |
| 2 | test2 | 20211016070806_trv.png | 2 | 220211016070806_trv.png | backd.png |
| 3 | test3 | | | | |
| 4 | test4 | | | | |
This is my dbfiddle.
Any suggestions how to add the image columns?
I appreciate your replies!

Answer 1

Try this:
Query #1
SELECT
Id,
Title,
File_Name,
listings_id,
MIN(front_image),
MIN(back_image)
FROM
(
SELECT
l.id,
l.title,
i.file_name,
i.listings_id,
CASE
WHEN i.properties = '[{"front_back":"front","path":null}]' THEN i.file_name
END AS front_image,
CASE
WHEN i.properties = '[{"front_back":"back","path":null}]' THEN i.file_name
END AS back_image,
i.properties FROM listings l
LEFT JOIN images i ON i.listings_id = l.id
ORDER BY l.id
) AS t1 GROUP BY id;
id
title
file_name
listings_id
MIN(front_image)
MIN(back_image)
1
test1
trv_front.png
1
trv_front.png
2_rv.png
2
test2
20211016070806_trv.png
2
20211016070806_trv.png
backd.png
3
test3
4
test4
View on DB Fiddle

Answer 2

Please use the case in your sql query :
Example is given below.
select l.id, l.title, i.file_name, i.listings_id,
CASE
WHEN i.properties = '[{"front_back":"front","path":null}]' THEN i.file_name
END AS front_image,
CASE
WHEN i.properties = '[{"front_back":"back","path":null}]' THEN i.file_name
END AS back_image,
i.properties from listings l
left join images i on i.listings_id = l.id order by l.id

Answer 3

Make use of JSON function in MySQL, JSON_EXTRACT(json_doc, path[, path] ...)
Returns data from a JSON document, selected from the parts of the document matched by the path arguments. Returns NULL if any argument is NULL or no paths locate a value in the document. An error occurs if the json_doc argument is not a valid JSON document or any path argument is not a valid path expression.
SELECT
a.id,
MAX(title) AS title,
GROUP_CONCAT(b.file_name) AS file_names,
MAX(b.listings_id) AS listings_id,
MAX(CASE WHEN JSON_EXTRACT(b.properties, '$[0].front_back') = 'front' THEN b.file_name ELSE NULL END) AS front_image,
MAX(CASE WHEN JSON_EXTRACT(b.properties, '$[0].front_back') = 'back' THEN b.file_name ELSE NULL END) AS back_image
FROM listings a
LEFT JOIN images b ON a.id = b.listings_id
GROUP BY a.id