MySQL : How to do a Matrix combining three tables - mysql

Question

I have the three following SQL Tables :
+-------------------------+
| SHOP |
+---------+---------------+
| shop_id | shop_label |
+---------+---------------+
| 1 | Shop Paris |
| 2 | Shop Madrid |
| 3 | Shop New York |
| 4 | Shop Tokyo |
+---------+---------------+
+----------------------------+
| PRODUCT |
+------------+---------------+
| product_id | product_label |
+------------+---------------+
| 1 | Pen |
| 2 | Workbook |
| 3 | Smartphone |
| 4 | Computer |
| 5 | Chair |
+------------+---------------+
+-------------------------------------------------------+
| COMMAND LINE |
+---------+------------+----------+---------------------+
| fk_shop | fk_product | quantity | date |
+---------+------------+----------+---------------------+
| 1 | 1 | 10 | 2021-10-20 12:10:59 |
| 4 | 3 | 1 | 2021-10-23 12:11:07 |
| 2 | 2 | 3 | 2021-10-29 12:12:07 |
| 1 | 2 | 8 | 2021-10-30 12:12:37 |
| 1 | 1 | 5 | 2021-11-03 13:10:07 |
+---------+------------+----------+---------------------+
And now I'm trying to make a matrix of all the products as COLUMNS and all the shops as ROWS showing how much product were buyed. I would like to make a query to retrieve this result :
+------------+------------+-------------+---------------+------------+
| | Shop Paris | Shop Madrid | Shop New York | Shop Tokyo |
+------------+------------+-------------+---------------+------------+
| Pen | 15 | 8 | | |
| Workbook | | 3 | | |
| Smartphone | | | | 1 |
| Computer | | | | |
| Chair | | | | |
+------------+------------+-------------+---------------+------------+
Do you know a way to do something like this ? I saw a long time ago a query with the WITH operator to create matrix, but I don't remember it really well...
Thanks for your help.

Answer 1

in oracle or sqlserver there is PIVOT() to use , but in MYSQL its not.
So something like this can be done:
select p.product_label ,
sum(case when s.shop_id = 1 then cl.quantity else 0 end) Shop_Paris ,
sum(case when s.shop_id = 2 then cl.quantity else 0 end) Shop_madrid ,
sum(case when s.shop_id = 3 then cl.quantity else 0 end) Shop_newyork ,
sum(case when s.shop_id = 4 then cl.quantity else 0 end) Shop_tokyo
from command_line cl
inner join product p on p.product_id = cl.fk_product
inner join shop s on s.shop_id = cl.fk_shop
group by p.product_label