SQL将一些列名转换为行值，将一个列名行值转换为列名

Posted 2023-04-12

【中文标题】SQL将一些列名转换为行值，将一个列名行值转换为列名

【英文标题】：SQL convert some column names to row values and one column name row values to column name

【发布时间】：2021-01-22 10:04:03

【问题描述】：

我有一个按如下方式组织的表格：

Year |Account | Location| Measure1 |Measure2 |Measure3 

2020 |123a    |A       |100      |20%        |5
2020 |234b    |B       |75       |80%        |8
2020 |122c    |C       |80       |78%        |9

我想创建如下记录：

Year  |Account | Measure      |A    |B     |C

2020  |123a     |Measure1    |100   |      |
2020  |
2020  |234b     |Measure2    |      |80%   |
2020  |122c     |Measure3    |      |      |9

【问题讨论】：

为什么预期结果集中的所有 3 条记录都与帐户 123a 关联？其他 2 个帐户怎么了？

解释第二行是如何出现的，只有一个年份的值。

【参考方案1】：

这个论坛不是为了解决你的编程任务。但是为了好玩：

select Year, Account, 'Measure1' as Measure, Measure1 as A, null as B, null as C
from my_table
where Location = 'A'

union

select Year, Account, 'Measure2' as Measure, Measure2 as A, null as B, null as C
from my_table
where Location = 'A'

...

union

select Year, Account, 'Measure1' as Measure, null as A, Measure1 as B, null as C
from my_table
where Location = 'B'

...

【参考方案2】：

我会推荐APPLY：

select t.year, t.account, v.*
from t cross apply
     (values ('Measure1', Measure1, null, null),
             ('Measure2', null, Measure2, null),
             ('Measure3', null, null, Measure3)
     ) v(measure, a, b, c);

这将返回除第二行之外的所有内容。目前尚不清楚您想要什么逻辑，但您可以添加：

union all
select distinct t.year, null, null, null, null, null

明确添加。