MySQL - 单个查询中的两个相关加权平均值 [英] MySQL - two dependent weighted averages in a single query

问题描述

这个问题扩展了上一个问题.除了一些单独的加权平均值之外，我还想添加一个加权平均值.

This question extends a previous question. I want to add a weighted average total in addition to some individual weighted averages.

我有一个 MySQL 表，如下所示:

I have a MySQL table which looks like this:

id  load_transit    load_standby    hours_transit   hours_standby
1   40              20              8               4
2   30              15              10              10
3   50              10              3               9

我需要做以下计算:

(中间计算)

hours_transit_total = 8+10+3 = 21
hours_standby_total = 4+10+9 = 23
hours_total = 21+23 = 44

(新的额外期望结果)

load_transit_weighted_mean = 40*(8/21) + 30*(10/21) + 50*(3/21) = 36.667
load_standby_weighted_mean = 20*(4/23) + 15*(10/23) + 10*(9/23) = 13.913
load_total_weighted_mean = 36.667*(21/44)+13.913*(23/44) = 24.772

是否可以在单个查询中执行此操作?最好的设计是什么?

Is it possible to do this in a single query? What would the best design be?

推荐答案

通过扩展我对您上一个问题的回答，这同样简单:

By extension of my answer to your previous question, this is just as simple:

SELECT sum(hours_transit * load_transit) / sum(hours_transit),
       sum(hours_standby * load_standby) / sum(hours_standby),
       (sum(hours_transit * load_transit + hours_standby * load_standby)) / sum(hours_transit + hours_standby)
FROM table1

这是对应的sqlfiddle.

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