MySQL选择列名作为字段 [英] MySQL select column name as field

问题描述

我有一个看起来像这样的mysql表:

I have a mysql table that looks something like this:

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:

I would like to be able to query on the id and get multiple rows, one for each column. E.g:

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

哪个会给我的?

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

我需要使用什么来制定这样的查询?

What would I need to use to formulate a query like this?

非常感谢

推荐答案

这称为枢轴.实际上，这是一个反向枢纽.有关某些背景，请参见此处. http://www.artfulsoftware.com/infotree/queries.php#78

This is called a pivot. Actually it's a reverse pivot. See here for some background. http://www.artfulsoftware.com/infotree/queries.php#78

MySQL很难做到.脖子很疼.许多在MySQL中从事此类工作的人都使用程序来生成这些查询.

MySQL does it the hard way. It's a pain in the neck. Many people who do lots of this kind of work in MySQL use programs to generate these queries.

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

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