MySQL 5.6

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CREATE TABLE Product (
  id INT AUTO_INCREMENT,
  name VARCHAR(64) UNIQUE,
  unit_price VARCHAR(6),
  PRIMARY KEY (id)
);

CREATE TABLE Sale (
  id INT AUTO_INCREMENT,
  product_id INT, created_at DATETIME,
  units INT, PRIMARY KEY (id),
  FOREIGN KEY (product_id) REFERENCES Product(id)
);

INSERT INTO Product(name, unit_price)
VALUES
('Methadone', 30),
('Codeine', 20),
('Morphine', 40),
('Fentanyl', 10);

INSERT INTO Sale(product_id, created_at, units)
VALUES
(1, '2004-01-06 08:27:25', 8),
(4, '2004-03-05 05:21:15', 24),
(2, '2005-01-06 08:26:55', 3),
(4, '2005-03-31 01:55:25', 6),
(1, '2005-11-09 11:33:20', 2),
(4, '2006-02-15 10:46:30', 4),
(3, '2006-04-14 07:40:50', 1),
(4, '2008-01-06 08:27:25', 5),
(4, '2008-01-10 21:31:45', 3),
(1, '2008-01-28 16:07:30', 9),
(3, '2008-03-05 05:21:00', 4),
(2, '2008-03-08 18:25:50', 5),
(4, '2008-05-02 02:15:20', 1),
(4, '2008-05-05 15:19:40', 3),
(4, '2008-06-28 23:08:55', 2),
(4, '2008-07-02 12:14:00', 2),
(3, '2008-08-29 09:07:50', 1),
(2, '2008-10-22 16:56:20', 5),
(3, '2008-10-26 06:01:25', 2),
(4, '2008-12-19 13:49:55', 4),
(2, '2008-12-23 02:55:30', 4),
(1, '2009-02-15 10:43:45', 4),
(2, '2009-04-14 07:37:50', 6),
(3, '2009-06-11 04:31:25', 3),
(4, '2009-08-08 01:25:30', 12),
(1, '2010-11-09 11:33:20', 8),
(1, '2011-01-14 10:22:35', 3),
(3, '2011-03-13 07:16:10', 3),
(4, '2011-05-10 04:10:15', 4),
(4, '2011-07-07 01:04:35', 4),
(4, '2011-09-02 21:58:10', 3),
(2, '2011-10-30 18:51:45', 3),
(1, '2011-12-27 15:45:20', 1),
(4, '2012-02-23 12:43:25', 2),
(4, '2012-04-21 09:37:30', 3),
(4, '2012-06-18 06:31:20', 1),
(2, '2012-08-15 03:25:40', 4),
(2, '2013-01-14 10:23:20', 4),
(4, '2013-02-01 05:01:35', 1),
(4, '2013-03-13 07:16:55', 1),
(4, '2013-03-31 01:55:10', 2),
(4, '2013-05-10 04:11:15', 2),
(3, '2013-05-27 22:48:45', 3),
(1, '2013-07-07 01:05:20', 3),
(2, '2013-07-24 19:42:20', 4),
(4, '2013-09-02 21:59:40', 4),
(3, '2013-09-20 16:36:10', 1),
(4, '2013-10-30 18:54:00', 2),
(4, '2013-11-17 13:29:45', 1),
(4, '2013-12-27 15:48:20', 3);

Records: 4  Duplicates: 0  Warnings: 0

Records: 50  Duplicates: 0  Warnings: 0

yr	best_seller	sales_amount
2013	Fentanyl,Codeine,Morphine	160
2012	Codeine	80
2011	Methadone,Morphine	120
2010	Methadone	240
2009	Methadone,Fentanyl,Codeine,Morphine	120
2008	Codeine,Morphine	280
2006	Morphine,Fentanyl	40
2005	Methadone,Codeine,Fentanyl	60
2004	Methadone,Fentanyl	240