我使用的mysql服务器示例有一定的限制（没有cte，不能创建临时表，甚至不能创建新表），所以唯一可以解决的方法就是使用派生表。
我有下表 t ，包含每个月（1-12）的每次销售事件：

+------+-----------+-----------------+
|  id  |  product  |  sold_on_month  |
+------+-----------+-----------------+
|   1  | Product 1 |        1        |
|   2  | Product 1 |        2        |
|   3  | Product 1 |        2        |
|   4  | Product 1 |        3        |
|   5  | Product 1 |        3        |
|   6  | Product 1 |        4        |
|   7  | Product 1 |        4        |
|   8  | Product 1 |        4        |
|   9  | Product 1 |        4        |
|  10  | Product 1 |        4        |
|  11  | Product 2 |        1        |
|  12  | Product 2 |        1        |
|  13  | Product 2 |        2        |
|  14  | Product 2 |        2        |
|  15  | Product 2 |        3        |
|  16  | Product 2 |        3        |
+------+-----------+-----------------+

我想创建一个查询，回答我按产品和月份销售了多少产品，如下所示：

+-----------+---------+------------+
|  product  |  month  |  how_many  |
+-----------+---------+------------+
| Product 1 |    1    |     1      |
| Product 1 |    2    |     2      |
| Product 1 |    3    |     2      |
| Product 1 |    4    |     5      |
| Product 1 |    5    |     0      |
| Product 1 |    6    |     0      |
| Product 1 |    7    |     0      |
| Product 1 |    8    |     0      |
| Product 1 |    9    |     0      |
| Product 1 |   10    |     0      |
| Product 1 |   11    |     0      |
| Product 1 |   12    |     0      |
| Product 2 |    1    |     2      |
| Product 2 |    2    |     2      |
| Product 2 |    3    |     2      |
| Product 2 |    4    |     0      |
| Product 2 |    5    |     0      |
| Product 2 |    6    |     0      |
| Product 2 |    7    |     0      |
| Product 2 |    8    |     0      |
| Product 2 |    9    |     0      |
| Product 2 |   10    |     0      |
| Product 2 |   11    |     0      |
| Product 2 |   12    |     0      |
+-----------+---------+------------+

到目前为止，我取得的成就是：如果我有一个没有列的类似表 product 如果我想按月份分组，问题是：

SELECT
  a.mn, COUNT(t.sold_on_month)
FROM
  (SELECT 1 AS mn UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8
   UNION SELECT 9 UNION SELECT 10 UNION SELECT 11 UNION SELECT 12) AS a
  LEFT JOIN t
    ON t.sold_on_month = a.mn
GROUP BY a.mn;

所以，我真正需要的是一个查询，它使用相同的派生表来计算月份，并按产品和销售月份分组，显示 0 在 how_many 当当月没有销售产品时。记住我不能使用cte或临时表。
感谢您的帮助！：）