MySQL选择列名作为字段

Question

我有一个mysql表,看起来像这样:

id | col_1 | col_2 | col_3
---|-------|-------|------
1  | 2     | 34    | 64
2  | 6     | 53    | 23

我希望能够查询id并获取多行,每列一行.例如:

SELECT column_name as column, column_value as value FROM my_table WHERE id=1;

哪个会给我:

column | value
-------|-------
col_1  | 2
col_2  | 34
col_3  | 64

我需要用什么来制定这样的查询？

非常感谢

Answer 1

这称为枢轴.实际上它是一个反向支点.在这里查看一些背景信息.http://www.artfulsoftware.com/infotree/queries.php#78

MySQL很难做到这一点.这是颈部疼痛.许多在MySQL中进行大量此类工作的人使用程序来生成这些查询.

SELECT `column`, column_value 
  FROM (
    SELECT id, 'col_1' as `column`, col_1 as column_value FROM tab
     UNION
    SELECT id, 'col_2' as `column`, col_2 as column_value FROM tab
     UNION
    SELECT id, 'col_3' as `column`, col_3 as column_value FROM tab
  ) pivot
  WHERE id=1