如何加上＆QUOT;权重和QUOT;到MySQL表，并根据这些选择随机值？ [英] How to add "weights" to a MySQL table and select random values according to these?

问题描述

我想创建一个表，其中包含某种权重中的每一行。然后，我要选择的概率等于（重量该行）/（重量全部行）随机值。例如，具有5列权重1,2,3,4,5出1000我会得到大约为1/15 * 1000 = 67次第一排等。

I want to create a table, with each row containing some sort of weight. Then I want to select random values with the probability equal to (weight of that row)/(weight of all rows). For example, having 5 rows with weights 1,2,3,4,5 out of 1000 I'd get approximately 1/15*1000=67 times first row and so on.

的表是手动填充。然后，我将采取从它的随机值。但我想有一个改变在灌浆期的概率能力。

The table is to be filled manually. Then I'll take a random value from it. But I want to have an ability to change the probabilities on the filling stage.

推荐答案

我发现这个的可爱的小算法在狴利贝特。你也许可以将其转换成一些程序上的SQL。

I found this nice little algorithm in Quod Libet. You could probably translate it to some procedural SQL.

function WeightedShuffle(list of items with weights):
  max_score ← the sum of every item’s weight
  choice ← random number in the range [0, max_score)
  current ← 0
  for each item (i, weight) in items:  
    current ← current + weight  
    if current ≥ choice or i is the last item:  
      return item i

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