本文介绍了在 SQL 计算中使用别名的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
为什么这个查询不起作用?
Why won't this query work?
SELECT 10 AS my_num, my_num*5 AS another_number
FROM table
在本例中，我尝试在其他计算中使用 my_num 别名.这导致未知列my_num"
In this example, I'm trying to use the my_num alias in other calculations. This results in unknown column "my_num"
这是我正在尝试做的简化版本，但基本上我想使用别名进行其他计算.我的计算要复杂得多，这就是为什么最好将其别名化，因为我以不同的方式重复了几次.
This is a simplified version of what I am trying to do, but basically I would like to use an alias to make other calculations. My calculations are much more complicated and thats why it would be nice to alias it since I repeat it several times different ways.
推荐答案
简单地用 (SELECT alias) 包裹你重复使用的别名:
Simply wrap your reused alias with (SELECT alias) :
SELECT 10 AS my_num,
(SELECT my_num) * 5 AS another_number
FROM table
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