[英]MySQL: Order by a function of two columns
I have two integer fields A and B in table T . 我在表T中有两个整数字段A和B.
I want to do something like " SELECT * FROM T ORDER BY f(A,B) DESC
" 我想做类似“
SELECT * FROM T ORDER BY f(A,B) DESC
”之类的事情
where f(A,B)
is a linear combination of A and B ... ie f(A,B) = mA + nB
, where m and n are numbers. 其中
f(A,B)
是A和B的线性组合......即f(A,B) = mA + nB
,其中m和n是数字。
What is the right syntax? 什么是正确的语法?
You have two options (at least): 你有两个选择(至少):
SELECT (n * A + m * B) AS C, *
FROM T
ORDER BY C DESC; -- or ORDER BY 1 DESC
Or: 要么:
SELECT *
FROM T
ORDER BY (n * A + m * B) DESC;
One or the other - possibly both - should work for you in MySQL. 一个或另一个 - 可能两者 - 应该在MySQL中为你工作。 The first should work even if the second does not.
第一个应该工作,即使第二个没有。
Try to keep it simple, use the following: 尽量保持简单,使用以下内容:
SELECT * FROM T ORDER BY (m * A + n * B) DESC
where m and n are on your responsibility. 其中m和n是你的责任。
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