mysql：按数字引用列

发布于 2024-11-30 19:16:23 字数 244 浏览 0 评论 0原文

我想给列别名，但不知道它们的名称，而只知道它们在表中的编号。

像这样的事情：

select firstColumn as myId, secondColumn as myName, thirdColumn as myLastName

我不知道列的实际名称

（我知道这种需求听起来很奇怪。是的，我可以知道列的名称。这是一个技术问题，如果您知道技术答案，请回答，无论动机如何！）

原文

I want to give columns aliases without knowing their names, but only their number in the table.

Something like this:

select firstColumn as myId, secondColumn as myName, thirdColumn as myLastName

where I don't know the actual names of the columns

(I understand that the need sounds strange. And yes I can know the names of the columns. This is a technical question, please answer if you know the technical answer, regardless of the motivation. Thank you!)

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白馒头 2024-12-07 19:16:23

您可以做的最接近的是使用 INFORMATION_SCHEMA.COLUMNS 从序数位置查找列名称。我知道这不是您所要求的，但我认为这可能是您能得到的最接近的。例如，您可以构建一个包含第一、第二和第五列的 select 语句，如下所示：

SELECT CONCAT("SELECT ",
   GROUP_CONCAT(column_name SEPARATOR ", "),
   " FROM ", table_name)
FROM information_schema.columns
WHERE table_schema = database() 
    AND table_name = 'my_table' 
    AND ordinal_position IN (1,2,5) 
GROUP BY table_name 
ORDER BY ordinal_position;

The closest you could do is use INFORMATION_SCHEMA.COLUMNS to find the column name from the ordinal position. I realize this isn't what you asked for, but I think it may be as close as you can get. For instance, you could build a select statement having the 1st, 2nd and 5th columns as follows:

SELECT CONCAT("SELECT ",
   GROUP_CONCAT(column_name SEPARATOR ", "),
   " FROM ", table_name)
FROM information_schema.columns
WHERE table_schema = database() 
    AND table_name = 'my_table' 
    AND ordinal_position IN (1,2,5) 
GROUP BY table_name 
ORDER BY ordinal_position;

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