asd, MySQL - rextester

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drop table if exists products;

CREATE TABLE products
(
date DATE,
productname VARCHAR(80),
quantity INT(5)
);

INSERT INTO `products`(`date`, `productname`, `quantity`) VALUES ('2016-12-16','toy',5);
INSERT INTO `products`(`date`, `productname`, `quantity`) VALUES ('2016-12-18','santa',8);
INSERT INTO `products`(`date`, `productname`, `quantity`) VALUES ('2016-12-23','tree',15);
INSERT INTO `products`(`date`, `productname`, `quantity`) VALUES ('2016-10-01','toy',10);
INSERT INTO `products`(`date`, `productname`, `quantity`) VALUES ('2016-10-04','santa',20);
INSERT INTO `products`(`date`, `productname`, `quantity`) VALUES ('2016-10-09','tree',30);
INSERT INTO `products`(`date`, `productname`, `quantity`) VALUES ('2016-10-01','toy',40);
INSERT INTO `products`(`date`, `productname`, `quantity`) VALUES ('2016-10-04','santa',30);
INSERT INTO `products`(`date`, `productname`, `quantity`) VALUES ('2016-10-09','tree',20);

select c.ym, 
	coalesce(santa,0) santa,
	coalesce(toy,0) toy,
	coalesce(tree,0) tree
from (
SELECT DATE_FORMAT(`date`, '%Y-%m') As ym,
  IFNULL(Sum(Case when `productname` = 'santa' then `quantity` end),0) As santa, 
  IFNULL(Sum(Case when `productname` = 'toy' then `quantity` end),0) As toy, 
  IFNULL(Sum(Case when `productname` = 'tree' then `quantity` end),0) As tree 
FROM `products`
GROUP BY DATE_FORMAT(`date`, '%Y-%m')
) t right join (select ym
from (
    select date_format(str_to_date('2016-10-01','%Y-%m-%d') + INTERVAL (a.a + (10 * b.a)) MONTH,'%Y-%m') as ym
    from (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as a
    cross join (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as b
) a
where ym between '2016-10' and '2016-12'
) c on t.ym = c.ym;


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