MYSQL: Separate products into columns - mysql

Question

This is in relation to my previous post MYSQL: Get quantity per product in each order.
Using the query below, it generates a table of:
SELECT o.order_id, o.username, op.product_id, SUM( op.quantity ) as quantity
FROM `orders` o JOIN
orders_products op
ON op.order_id = o.order_id
GROUP BY op.product_id, o.order_id
ORDER BY o.order_id, op.product_id;
_______________________________________________
| order_id | username | product_id | quantity |
-----------------------------------------------
| 1 | bill | 1 | 5 |
-----------------------------------------------
| 1 | bill | 2 | 3 |
-----------------------------------------------
| 1 | bill | 3 | 2 |
-----------------------------------------------
| 2 | sally | 1 | 2 |
-----------------------------------------------
| 3 | jeff | 1 | 6 |
-----------------------------------------------
| 3 | jeff | 2 | 7 |
-----------------------------------------------
As seen above, each new product_id is assigned its own row. Is it possible to have additional columns for each product_id instead of rows generating an output same as the one below?
_______________________________________________________________________
| order_id | username | product_qty_1 | product_qty_2 | product_qty_3 |
-----------------------------------------------------------------------
| 1 | bill | 5 | 3 | 2 |
-----------------------------------------------------------------------
| 2 | sally | 2 | 0 | 0 |
-----------------------------------------------------------------------
| 3 | jeff | 6 | 7 | 0 |
-----------------------------------------------------------------------
My tables:
-- Orders
_______________________
| order_id | username |
-----------------------
| 1 | bill |
-----------------------
| 2 | sally |
-----------------------
| 3 | jeff |
-----------------------
-- Products
___________________
| id | product |
-------------------
| 1 | Table |
-------------------
| 2 | Chair |
-------------------
| 3 | Mouse |
-------------------
-- Order Products
___________________________________________
| id | order_id | product_id | quantity |
-------------------------------------------
| 1 | 1 | 1 | 5 |
-------------------------------------------
| 2 | 1 | 2 | 3 |
-------------------------------------------
| 3 | 1 | 3 | 2 |
-------------------------------------------
| 4 | 2 | 1 | 2 |
-------------------------------------------
| 5 | 3 | 1 | 6 |
-------------------------------------------
| 6 | 3 | 2 | 7 |
-------------------------------------------

Answer 1

If you know the products in advance, you can use conditional aggregation:
SELECT o.order_id, o.username,
SUM(CASE WHEN op.product_id = 1 THEN op.quantity ELSE 0 END) as quantity1,
SUM(CASE WHEN op.product_id = 2 THEN op.quantity ELSE 0 END) as quantity2,
SUM(CASE WHEN op.product_id = 3 THEN op.quantity ELSE 0 END) as quantity3
FROM `orders` o JOIN
orders_products op
ON op.order_id = o.order_id
GROUP BY o.order_id
ORDER BY o.order_id;
If you don't know the product ids, then you would have to use dynamic SQL, or perhaps use GROUP_CONCAT() to create a string with the information you want.