整个时间按类别划分的 MySQL 成本

Question

我有一个如下所示的表格：

Site | Category | Cost | Month |
A    | Hardware | 10   | 1     |
A    | Software | 30   | 1     |
B    | Software | 15   | 1     |
C    | Labor    | 5    | 2     |
...

我需要输出这个：

Site | Category |  1   |  2  | ...
A    | Hardware | 10   |  0  |
A    | Software | 30   |  0  |
B    | Software | 15   |  0  |
C    | Labor    |  0   |  5  |

将 Month 属性下的记录用作列标题并在其对应的 Month 列下分配 Cost 记录的最佳方法是什么？

Answer 1

SELECT Site, Category, 
   IF(Month=1,Cost,0) as M1,
   IF(Month=2,Cost,0) as M2,
   IF(Month=3,Cost,0) as M3,
   IF(Month=4,Cost,0) as M4,
   IF(Month=5,Cost,0) as M5,
   IF(Month=6,Cost,0) as M6,
   IF(Month=7,Cost,0) as M7,
   IF(Month=8,Cost,0) as M8,
   IF(Month=9,Cost,0) as M9,
   IF(Month=10,Cost,0) as M10,
   IF(Month=11,Cost,0) as M11,
   IF(Month=12,Cost,0) as M12
FROM tablename

会逐行给出。如果您希望每个 Category 有一行，可以添加 GROUP BY

SELECT Site, Category, 
   SUM(IF(Month=1,Cost,0)) as M1,
   SUM(IF(Month=2,Cost,0)) as M2,
   SUM(IF(Month=3,Cost,0)) as M3,
   SUM(IF(Month=4,Cost,0)) as M4,
   SUM(IF(Month=5,Cost,0)) as M5,
   SUM(IF(Month=6,Cost,0)) as M6,
   SUM(IF(Month=7,Cost,0)) as M7,
   SUM(IF(Month=8,Cost,0)) as M8,
   SUM(IF(Month=9,Cost,0)) as M9,
   SUM(IF(Month=10,Cost,0)) as M10,
   SUM(IF(Month=11,Cost,0)) as M11,
   SUM(IF(Month=12,Cost,0)) as M12
FROM tablename
GROUP BY Site, Category

将保留网站，但总结类别。

另外，如果您不喜欢该字段的 Mx 名称，您可以尝试使用 '1' .. '2' 等。我认为它应该可以工作