https://www.youtube.com/watch?v=o5W-iAK21ws&list=PLavw5C92dz9Hxz0YhttDniNgKejQlPoAn&index=9

drop TABLE if exists orders;
CREATE TABLE orders 
(
	customer_id 	INT,
	dates 			DATE,
	product_id 		INT
);
INSERT INTO orders VALUES
(1, '2024-02-18', 101),
(1, '2024-02-18', 102),
(1, '2024-02-19', 101),
(1, '2024-02-19', 103),
(2, '2024-02-18', 104),
(2, '2024-02-18', 105),
(2, '2024-02-19', 101),
(2, '2024-02-19', 106); 

select * from orders;

UNION_UNION ALL
GROUP_CONCAT()

SELECT dates,product_id AS Products FROM orders
UNION
SELECT dates, GROUP_CONCAT(product_id)FROM orders
GROUP BY customer_id,dates
ORDER BY dates,products