Question

女士们，先生们，

我在MySQL 5.1中遇到以下问题。这是我的桌子。

Sale | Store | Product | Discount
---------------------------------
 1   |   1   |   B     | Yes
 2   |   1   |   B     | Yes
 3   |   1   |   B     | No
 4   |   1   |   D     | Yes
 5   |   1   |   A     | No
 6   |   2   |   A     | No
 7   |   3   |   B     | No
 8   |   3   |   B     | No
 9   |   1   |   D     | Yes
10   |   2   |   A     | No

现在这当然是一种非常不方便的组织数据的方式，但这就是数据发生的方式（并将继续进入）。

我需要能够将完全随意的产品类型列表（如果你愿意，可以用逗号分隔）;让我们说A,B,C。最后，我需要一个什么商店出售的清单。这是一个中间结果，使其更容易理解。

Store | Product | Sales | Discounts
-----------------------------------
  1   |   A     |  1    | 0
  1   |   B     |  3    | 2
  1   |   C     |  0    | 0
  2   |   A     |  2    | 0
  2   |   B     |  0    | 0
  2   |   C     |  0    | 0
  3   |   A     |  0    | 0
  3   |   B     |  2    | 0
  3   |   C     |  0    | 0

我最终需要的是：

Store | Product types sold | Discounts given on product types:
-------------------------------------------------------------
  1   |         2          |        1
  2   |         1          |        0
  3   |         1          |        0

第三栏显示有多少已售出（和查询）的产品类型至少获得一次折扣。

我尝试过各种动态交叉生成查询（是的，我已经看过它们了），但是我没有足够的心理RAM来一次性包裹所有内容。您如何以最有效的方式处理这个问题？临时表/存储过程等是可以的，非常欢迎粗略的想法。谢谢！

Answer 1

您可以按商店和产品对数据进行分组，以产生中间结果：

mysql> SELECT Store, Product,
COUNT(1) AS Sales,
SUM(IF(Discount='Yes', 1, 0)) AS Discounts
FROM input
WHERE Product IN ('A', 'B', 'C', 'D')
GROUP BY Store, Product
+-------+---------+-------+-----------+
| Store | Product | Sales | Discounts |
+-------+---------+-------+-----------+
|     1 | A       |     1 |         0 |
|     1 | B       |     3 |         2 |
|     1 | D       |     2 |         2 |
|     2 | A       |     2 |         0 |
|     3 | B       |     2 |         0 |
+-------+---------+-------+-----------+
5 rows in set (0.00 sec)

然后，您可以仅按商店对此结果进行分组，将其转换为最终结果：

mysql> SELECT Store,
COUNT(1) AS `Product types sold`,
SUM(Discounts) AS `Discounts given on product types`
FROM (
SELECT Store, Product,
COUNT(1) AS Sales,
SUM(IF(Discount='Yes', 1, 0)) AS Discounts
FROM input
WHERE Product IN ('A', 'B', 'C', 'D')
GROUP BY Store, Product
) AS intermediate
GROUP BY Store
+-------+--------------------+----------------------------------+
| Store | Product types sold | Discounts given on product types |
+-------+--------------------+----------------------------------+
|     1 |                  3 |                                4 |
|     2 |                  1 |                                0 |
|     3 |                  1 |                                0 |
+-------+--------------------+----------------------------------+
3 rows in set (0.00 sec)

请注意，第一个查询是第二个查询的子查询。

Answer 2

我认为分离查询最简单：

select Store, 
   (Select count( distinct Product) from products as p2 where p2.Store = p1.Store),
   (Select count(distinct Product) from products as p3 where p3.Store = p1.Store and p3.Discount = "Yes")
from products p1
group by Store

（如果是大表，请务必测试您的表现。）

MySQL动态交叉表超过两列

2 个答案: