mysql - 我们如何在 MySQL 中的这种情况下进行旋转

Question

我有这张桌子：

+----------+--------+-----+--------+--------+
| personId | Name   | Age | height | weight |
+----------+--------+-----+--------+--------+
| 1        | Aritra | 20  | 5.6    | 56     |
| 1        | Aritra | 30  | 5.6    | 76     |
+----------+--------+-----+--------+--------+

但要求输出是这样的：

+---------------+----------+--------------+----------+
| AttributeName | personId | Presentvalue | OldValue |
+---------------+----------+--------------+----------+
| Height        | 1        | 5.6          | 5.6      |
| weight        | 1        | 76           | 56       |
+---------------+----------+--------------+----------+

我试图使用枢轴来实现这一点，但遇到了问题。无论使用或不使用枢轴，我该如何做到这一点？

谢谢你。

Answer 1

union all可能是最简单的方法：

select 'Height' as attributeName, personId,
       (case when age = 30 then height end) as newValue,
       (case when age = 20 then height end) as oldValue
from t 
union all
select 'Weight' as attributeName, personId,
       (case when age = 30 then weight end) as newValue,
       (case when age = 20 then weight end) as oldValue;